I-NRLF 


^  sob  mo 


Minmg  dept. 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


Class 


THE 

CHEMICAL  ANALYSIS  OF  IRON 


A    COMPLETE   ACCOUNT   OF   ALL   THE    BEST 
KNOWN    METHODS 


Analysis  of  Iron,  Steel,  Pig-Iron,  Iron  Ore,  Limestone, 

Slag,  Clay,  Sand,  Coal,  Coke,  and  Furnace 

and  Producer  Gases 


BY 

ANDREW  ALEXANDER   BLAIR 

fi 

GRADUATE  UNITED   STATES   NAVAL  ACADEMY,    l866 ;    CHIEF  CHEMIST  UNITED  STATES   BOARD  APPOINTED  TO 

TEST   IRON,   STEEL,  AND  OTHER   METALS,    1875  ;   CHIEF  CHEMIST  UNITED  STATES  GEOLOGICAL 

SURVEY  AND  TENTH   CENSUS,    l88o  ;   MEMBER  AMERICAN  PHILOSOPHICAL 

SOCIETY,   ETC. 


SIXTH  EDITION 


PHILADELPHIA  AND  LONDON 

J.   B.   LIPPINCOTT    COMPANY 
1906 


MINIM* 


Copyright,  1888,  by  ANDREW  ALEXANDER  BLAIR, 


Copyright,  1891,  by  ANDREW  ALEXANDER  BLAIR, 


Copyright,  1896,  by  ANDREW  ALEXANDER  BLAIR. 


Copyright,  1901,  by  ANDREW  ALEXANDER  BLAIR, 


Copyright,  1902,  by  ANDREW  ALEXANDER  BLAIR. 


Copyright,  1906,  by  ANDREW  ALEXANDER  BLAIR. 


ELECTROTVPISO  ANO  PR'NTEO  BY  J.  B.  UPPINCOTT  COMPANY,  PHILADELPHIA,  U.S.A. 


TO 

MY    WIFE 

WITHOUT   WHOSE   ASSISTANCE  IT    WOULD   NEVER   HAVE 
BEEN  WRITTEN 

'THIS   VOLUME 

IS 

2>eDtcateD 


154700 


PREFACE  TO  THE  SIXTH  EDITION. 


THE  changes  in  this  edition  are  principally  in  the  methods  for 
the  determination  of  carbon  in  iron,  steel,  and  special  alloys. 
There  has  been  added  a  special  chapter  on  chrome-tungsten  steels 
and  one  on  ferro-tungsten  and  tungsten  metal.  The  importance 
of  the  alloys  of  the  rarer  metals,  tungsten,  chromium,  nickel, 
vanadium,  and  molybdenum,  seems  to  be  constantly  increasing, 
and  the  best  methods  for  their  determination  and  separation  from 
one  another  should  be  at  the  command  of  the  analyst. 

PHILADELPHIA,  May,   1906. 


/  £ 

PREFACE  TO  THE  FIFTH  EDITION 


VERY  few  differences  will  be  found  between  this  and  the 
fourth  edition.  Some  minor  corrections,  the  insertion  of  Wal- 
ters's  method  for  the  color  determination  of  manganese,  and  the 

o 

description  of  the  Shimer  crucible  for  carbon  determination  being 
practically  all  the  changes  considered  necessary. 

PHILADELPHIA,  December,   1902. 


PREFACE  TO  THE   FOURTH   EDITION. 


THE  number  of  improved  methods  available,  the  use  of  new 
materials  in  technical  work,  and  the  general  advance  in  chemical 
knowledge  necessitated  so  many  changes  that  in  preparing  the 
fourth  edition  of  this  work  I  decided  to  rewrite  it  entirely.  In 
doing  this  I  have  substituted  chemical  terms  for  formulas  in  the 
text,  omitted  the  marginal  notes,  and  changed  the  nomenclature 
to  coincide  with  that  in  general  use.  I  hope  that  these  changes 
will  recommend  themselves  to  the  users  of  the  book.  The 
prompt  and  generous  response  to  requests  for  information  from 
members  of  my  profession  is  shown  in  the  foot-notes. 

The  entire  labor  of  proof-reading  and  index-making  has,  by 
my  enforced  absence,  been  thrown  on  my  friend  and  co-worker, 
Mr.  J.  Edward  Whitfield,  to  whom  this  brief  acknowledgment  is 
but  a  poor  indication  of  the  weight  of  my  obligation. 

BoRDIGHERA,  January,    1901. 


PREFACE  TO  THE  THIRD   EDITION. 


SUCH  changes  as  were  necessary  to  bring  the  methods  for 
the  determination  of  the  various  elements  in  accord  with  the 
present  state  of  the  science  have  been  made  in  this  edition. 

The  method  for  the  "  Volumetric  Determination  of  Phos- 
phorus in  Steel"  is  that  worked  out  by  the  Sub-Committee  on 
Standards  of  the  International  Steel  Standards  Committee,  and 
as  such  is  merely  tentative.  Its  publication  here  is  not  official, 
but  through  the  courtesy  of  the  committee  it  is  placed  before 
the  profession  in  the  hope  that  criticism  may  confirm  its  value 
or  point  out  its  errors.  The  modifications  in  the  method  for 
the  determination  of  sulphur  in  pig-iron  are  improvements,  but 
no  method  is  perfectly  satisfactory.  Two  new  methods  for  the 
determination  of  carbon  are  given,  and  some  modifications  of 
Volhard's  method  for  the  determination  of  manganese  in  high 
grade  manganese  ores  are  introduced. 

Many  minor  changes  have  been  made,  and  it  is  hoped  that 
this  edition  may  meet  the  same  cordial  reception  as  the  two 
former. 

LABORATORY  OF  BOOTH,  GARRETT  &  BLAIR, 
PHILADELPHIA,  September,  1896. 


PREFACE  TO  THE  SECOND   EDITION. 


IN  preparing  the  second  edition  of  this  book  I  have  tried  to 
correct  the  mistakes  that  were  apparent  in  the  first  edition,  and  to 
add  such  matter  as  the  advance  in  analytical  chemistry  seemed  to 
justify.  In  effecting  the  first  of  these  objects  I  have  been  aided 
by  such  kindly  criticism  as  the  profession  and  reviews  offered  me, 
and  in  the  second  by  the  advice  and  assistance  of  many  of  my 
fellow-workers.  Among  others  my  thanks  are  due  to  Messrs. 
Maunsel  White  and  A.  L.  Colby,  of  the  Bethlehem  Iron  Company  ; 
Mr.  Clemens  Jones,  of  the  Thomas  Iron  Company  ;  Mr.  E.  F. 
Wood,  of  the  Homestead  Steel-Works  ;  Mr.  T.  T.  Morrell,  of  the 
Cambria  Iron  Company  ;  Mr.  H.  C.  Babbitt,  of  the  Wellman  Steel 
Company ;  Prof.  F.  W.  Clarke,  Chief  Chemist  U.  S.  Geological 
Survey  ;  Mr.  J.  E.  Stead,  of  Middlesborough,  England  ;  and  Mr. 
J.  Edward  Whitfield,  of  Philadelphia. 

It  will  be  seen  that  the  "Table  of  Atomic  Weights"  has  been 
revised  ;  the  latest  and  most  reliable  values  for  the  elements  are 
given,  and  the  "Table  of  Factors"  has  been  changed  to  corre- 
spond to  these  values. 

LABORATORY  OF  BOOTH,  GARRETT  &  BLAIR, 
PHILADELPHIA,  June,   1891. 


PREFACE  TO  THE  FIRST  EDITION. 


THE  various  methods  for  the  analysis  of  iron  and  steel,  as  well 
as  the  descriptions  of  special  apparatus  to  facilitate  the  perform- 
ance of  the  analytical  work,  are  so  widely  distributed  through 
transactions  of  societies,  journals,  reviews,  periodicals,  and  works 
on  general  analytical  chemistry  that  only  the  possessor  of  a 
chemical  library  can  command  the  literature  of  the  subject.  It 
is  my  object  in  the  following  pages  to  bring  within  the  compass 
of  a  single  volume,  as  nearly  as  possible,  all  the  methods  of  real 
value  to  the  iron  analyst,  and  in  doing  this  to  give  the  credit  of 
originality  for  the  different  methods  and  improvements  to  the 
proper  persons.  In  many  cases  this  has  been  very  difficult,  and 
I  shall  be  glad  to  have  any  mistake  brought  to  my  attention. 

This  work  presupposes  some  knowledge  of  general  and 
analytical  chemistry,  and  some  practical  experience  in  laboratory 
work  and  manipulation,  as  it  is  intended  to  be  a  guide  for  the 
student  of  iron  chemistry  only.  For  such  persons  the  details  of 
the  descriptions  of  the  methods  will,  I  hope,  often  prove  of  great 
assistance.  With  very  few  exceptions,  these  descriptions  are  the 
results  of  my  own  experience  in  the  use  of  the  methods,  and  the 
details  are  those  that  seemed  to  me  to  be  of  importance  in  their 
practical  performance.  Many  of  the  special  forms  of  apparatus 
are  of  my  own  contrivance  ;  they  have  proved  extremely  useful 
to  me,  and  I  hope  may  facilitate  in  some  cases  the  work  of  iron 
chemists,  to  whom  often  very  little  is  given  and  of  whom  very 
much  is  required. 


CONTENTS. 


PAGE 

APPARATUS ii 

APPARATUS  FOR  THE  PREPARATION  OF  THE  SAMPLES n 

GENERAL  LABORATORY  APPARATUS 18 

REAGENTS <|| 37 

ACIDS  AND  HALOGENS,  38.     GASES,  42.     ALKALIES  AND  ALKALINE  SALTS,  44. 
SALTS  OF  ALKALINE   EARTHS,  51.     METALS  AND  METALLIC   SALTS,  53. 
REAGENTS  FOR  DETERMINING  PHOSPHORUS,  59. 
METHODS  FOR  THE  ANALYSIS  OF  PIG-IRON,  BAR-IRON,  AND  STEEL    60 

DETERMINATION  OF  SULPHUR.  By  evolution  as  Hydrogen  Sulphide.  Absorp- 
tion by  alkaline  solution  of  lead  nitrate,  60  ;  by  ammoniacal  solution  of  cad- 
mium sulphate,  63 ;  by  ammoniacal  solution  of  silver  nitrate,  63.  Absorp- 
tion and  oxidation  by  bromine  and  hydrochloric  acid,  64  ;  by  potassium 
permanganate,  65  ;  by  hydrogen  peroxide,  65.  By  oxidation  and  solution, 
66.  Bamber's  method  for  pig-iron,  67.  Special  precautions  in  the  determi- 
nation of  sulphur  in  pig-irons,  67.  RAPID  METHODS.  Volumetric  deter- 
mination by  iodine,  68. 

DETERMINATION  OF  SILICON,  72.  By  solution  in  nitric  and  hydrochloric  acids, 
72  ;  in  nitric  and  sulphuric  acids,  73.  By  volatilization  in  a  current  of 
chlorine  gas,  73.  RAPID  METHOD,  77. 

DETERMINATION  OF  SLAG  AND  OXIDES,  78.  By  solution  in  iodine,  78.  By 
volatilization  in  a  current  of  chlorine  gas,  80. 

DETERMINATION  OF  PHOSPHORUS,  80.  The  acetate  method,  80.  When  tita- 
nium ts present,  85.  The  molybdate  method,  88.  The  combination  method, 
91.  When  titaniiim  is  present,  92.  RAPID  METHODS,  92.  Volumetric 
method,  92.  Alkalimetric  method,  104.  Direct  weighing  of  the  phospho- 
molybdate,  106. 

DETERMINATION  OF  MANGANESE,  108.  The  acetate  method,  108.  General 
remarks  on  the  acetate  method,  112.  The  nitric  acid  and  potassium  chlorate 
method  (Ford's),  113.  Steels  containing  much  silicon,  115.  Pig-iron,  115. 
Spiegel  and  ferro-manganese,  irs.  RAPID  METHODS,  116.  Volumetric 
methods.  Volhard s  method,  116.  Williams' s  method,  118.  Bismuthate 
method,  121.  De shays }s  method,  128.  The  color  method  (for  steel),  129. 
Walters"  s  modification,  131. 

DETERMINATION  OF  CARBON,  132.  TOTAL  CARBON,  132.  Direct  combustion  in 
a  current  of  oxygen,  134.  Direct  combustion  in  a  Gooch  tubulated  crucible, 
139.  Combustion  with  lead  chromate  and  potassium  chlorate,  143  ;  with 
cupric  oxide  in  a  current  of  oxygen,  145.  Solution  and  oxidation  in  sul- 
phuric, chromic,  and  phosphoric  acids,  the  volume  of  the  carbonic  acid  being 
measured,  146  ;  the  carbonic  acid  being  weighed,  149.  Volatilization  of  the 
iron  in  a  current  of  chlorine,  and  subsequent  combustion  of  the  residue,  151. 
Volatilization  of  the  iron  in  a  current  of  hydrochloric  acid  gas,  and  subse- 

xvii 


CONTENTS. 

PAGE, 

quent  combustion  of  the  residue,  156.  Solution  in  potassium-cupric  chlor- 
ide, filtration,  and  weighing  or  combustion  of  the  residue,  156.  Modification 
by  Job  and  Davies,  166.  Repeated  use  of  potassium-cupric  chloride  for  the 
solution  of  steel,  170.  Combustion  in  the  Shimer  crucible,  171.  Solution  in 
cupric  sulphate,  filtration,  and  combustion  of  the  residue  in  a  current  of  oxy- 
gen, 173.  Solution  in  cupric  sulphate,  and  oxidation  of  the  residue  by  chro- 
mic and  sulphuric  acids,  174. 

DETERMINATION  OF  GRAPHITIC  CARBON 174 

DETERMINATION  OF  COMBINED  CARBON,   175.      Indirect  method,    175.     Direct 

method  (color  method),  175. 

DETERMINATION  OF  TITANIUM,  184.     By  precipitation,  184.     By  volatilization, 
185. 

DETERMINATION  OF  COPPER 185 

DETERMINATION    OF    NICKEL    AND    COBALT,  188.     The  acetate  method,  188. 

The  ether  method,  191. 
DETERMINATION    OF    CHROMIUM,  193.     The  ether  method,  194.     Volumetric 

method,  194.     Barba  s  modification,  195. 

DETERMINATION  OF  ALUMINUM,  196.     Stead's  method,  196.     Carnot's  method, 
197.     Ether  method,  198. 

DETERMINATION  OF  ARSENIC 199 

DETERMINATION  OF  TIN .    200 

DETERMINATION  OF  TUNGSTEN 201 

DETERMINATION  OF  VANADIUM 202 

DETERMINATION   OF   MOLYBDENUM,  205.     In   ferro-molybdenum,  206.     Rapid 
method,  206. 

DETERMINATION  OF  NITROGEN 207 

DETERMINATION  OF  IRON 210 

METHODS  FOR  THE  ANALYSIS  OF  CHROME-TUNGSTEN  STEELS   ...    211 

DETERMINATION  OF  CARBON      211 

DETERMINATION  OF  SULPHUR 211 

DETERMINATION  OF  SILICON  AND  TUNGSTEN 211 

DETERMINATION  OF  PHOSPHORUS 212 

DETERMINATION  OF  MANGANESE 212 

DETERMINATION  OF  CHROMIUM 212 

DETERMINATION  OF  NICKEL,  CHROMIUM  AND  MANGANESE 213 

DETERMINATION  OF  VANADIUM,  213.     Separation  of  Chromium  and  Vanadium  214 
METHODS  FOR  THE  ANALYSIS  OF  FERRO-TUNGSTEN  AND  TUNGSTEN 

METAL , 215 

DETERMINATION  OF  CARBON 215 

DETERMINATION  OF  TUNGSTEN 215 

DETERMINATION  OF  THE  OTHER  ELEMENTS 216 

DETERMINATION  OF  SULPHUR 216 

METHODS  FOR  THE  ANALYSIS  OF  FERRO-CHROME,  FERRO-SILICON, 

AND  FERRO-TITANIUM     217 

DETERMINATION  OF  CARBON 217 

DETERMINATION  OF  SULPHUR 217 

DETERMINATION  OF  SILICON 218 

DETERMINATION  OF  PHOSPHORUS,  219.     In  ferro-chrome,  219.     In  ferro-silicon, 

219.     In  ferro-titanium,  220. 
xviii 


CONTENTS. 

PAGE. 

DETERMINATION  OF  MANGANESE •  >   •    22° 

DETERMINATION  OF  CHROMIUM,  220.      Gravimetric  method,  220.    Volumetric 

method 221 

DETERMINATION  OF  IRON 221 

METHODS  FOR  THE  ANALYSIS  OF  IRON  ORES 222 

Remarks  on  sampling,  222.  Determination  of  hygroscopic  water,  223.  Deter- 
mination of  total  iron,  224.  Methods  of  standardizing  the  solutions,  229. 
Determination  of  ferrous  oxide,  233.  Of  sulphur,  237.  Of  phosphoric  acid, 
239.  Of  titanic  acid,  241.  Of  manganese,  242.  Pattinsori s  method,  244. 
Determination  of  manganese  dioxide,  245.  Bunseri 's  method,  246.  By 
ferrous  sulphate,  247. 
DETERMINATION  OF  SILICA,  ALUMINA,  LIME,  MAGNESIA,  MANGANESE  OXIDE, 

AND  BARYTA 248 

DETERMINATION  OF  SILICA,  256.    Separation  of  alumina  and  ferric  oxide,  257. 

DETERMINATION  OF  NICKEL,  COBALT,  ZINC,  and  MANGANESE,  260 ;  of  copper, 

lead,  arsenic,  and  antimony,  261  ;  of  the  alkalies,  264  ;  of  carbonic  acid,  265  ; 

of  combined  water  and  carbon  in  carbonaceous'  matter,  267  ;  of  chromium, 

270  ;  of  tungsten,  272  ;  of  vanadium,  272  ;  of  the  specific  gravity,  272. 

METHODS  FOR  THE  ANALYSIS  OF  LIMESTONE 274 

METHODS  FOR  THE  ANALYSIS  OF  CLAY   .    .    .    . ' 278 

METHODS  FOR  THE  ANALYSIS  OF  SLAGS 283 

METHOD  FOR  THE  ANALYSIS  OF  FIRE-SANDS 287 

METHODS  FOR  THE  ANALYSIS  OF  COAL  AND  COKE 288 

Proximate  analysis,  288.     Determination  of  volatile  combustible  matter,  289.   Of 
ash,  290.     Of  fixed  carbon,  290.    Of  sulphur,  290.  By  Eschkci1  s  method,  291. 
DETERMINATION  OF  PHOSPHORIC  ACID,  293.     Ultimate  analysis,  294.     Heating 
effect,  295. 

METHODS  FOR  THE  ANALYSIS  OF  GASES 297 

Collecting  samples,  297.  Reagents  for  the  pipettes,  300.  Analysis  of  the  sam- 
ple, 302. 

DETERMINATION  OF  CARBONIC  ACID,  304.  Of  oxygen,  304.  Of  carbonic 
oxide,  304.  Of  hydrogen,  305.  Of  methane,  307.  Of  nitrogen,  309.  Ex- 
ample of  calculation,  310. 

TABLES 311 

Table  I.  Atomic  weights  of  the  elements,  311.  Table  II.  Table  of  factors,  312. 
Table  III.  Percentages  of  phosphorus  and  phosphoric  acid  for  each  milli- 
gramme of  magnesium  pyrophosphate,  314.  Table  IV.  Tension  of  aqueous 
vapor,  315.  Table  V.  Table  for  reducing  volumes  of  gases  to  the  normal 
stRte,  316. 

INDEX - 323 

xix 


THE  CHEMICAL  ANALYSIS  OF  IRON. 


APPARATUS. 

THE  speed  and  facility  with  which  results  may  be  obtained,  and  often 
the  accuracy  of  these  results,  are  dependent  upon  various  mechanical 
appliances  as  well  as  upon  the  skill  of  the  analyst.  These  appliances  will 
be  considered  under  separate  heads. 

APPARATUS  FOR  THE  PREPARATION   OF  THE  SAMPLES. 

For  crushing  iron  ores,  a  mortar  and  pestle,  such  as  are  ordinarily 
used,  have  caused  much  trouble.  In  breaking  up  hard  ores  the  wear, 
especially  on  the  pestle,  is  considerable,  and  the  particles  of  cast  iron  may 
cause  the  sample  to  yield  too  high  a  result  in  the  determination  of  metallic 
iron.  Of  course,  in  non-magnetic  ores  these  particles  may  be  removed 
with  a  magnet,  but  in  the  case  of  magnetic  or  partly  magnetic  ores  this 
cannot  be  done,  and  a  hardened  steel  mortar  and  pestle  should  be  used. 
The  sample  should  be  broken  to  about  pea  size,  well  mixed,  and  quartered, 
this  quarter  broken  still  finer,  and  mixed  and  quartered  in  the  same  way 
until  the  resulting  portion  is  small  enough  to  be  bottled.  The  final  grind- 
ing can  be  best  done  on  a  chilled-iron  plate  with  a  hardened  steel  muller. 
Except  with  unusually  refractory  ores,  further  grinding  is  unnecessary, 
but  with  such  ores  the  final  grinding  must  be  in  an  agate  mortar.  In  large 
laboratories  and  where  many  ores  are  analyzed,  arrangements  such  as  are 
shown  in  the  accompanying  sketches  will  prove  very  useful.  Fig.  I  shows 
a  steel  mortar,  the  pestle  worked  by  power,  and  a  chilled  plate  and  muller. 

ii 


12 


APPARATUS  FOR    THE   PREPARATION  OF   THE   SAMPLES. 


A  is  the  mortar ;  B,  a  wooden  stem  in  which  the  pestle  fits.  The  cams 
H  fit  on  the  shaft  and  raise  the  pestle  by  means  of  the  tappets  a,  which 
are  faced  with  raw  hide.  An  iron  hoop  shrunk  on  the  mortar  has  a  ring, 
in  which  is  fastened  the  lower  block  of  the  pulley  D ;  the  upper  block  is 
attached  to  a  traveller,  E.  When  in  use  the  mortar  is  covered  with  a 
leather  cap,  which  prevents  the  pieces  of  ore  from  flying  out  of  the  mortar. 
To  transfer  the  powdered  ore  to  the  chilled  plate  F,  remove  the  leather  cap, 
raise  the  pestle  clear  of  the  mortar,  and  fasten  it  up  by  a  hook  from  the 

FIG.  i. 


framework  to  the  tappet  a.  Raise  the  mortar  by  pulling  the  fall  from  the 
upper  block  and  fastening  the  hook  in  its  end  into  a  ring  at  the  lower  block. 
By  means  of  the  traveller,  run  the  mortar  over  the  plate  and  turn  the  ore 
out.  After  quartering  the  sample  down,  finish  the  grinding  on  the  chilled 
plate  with  the  muller  C.  The  sheet-iron  troughs  G  serve  to  catch  any 
ore  that  falls  from  the  plate.  In  some  laboratories  a  small  Blake  crusher 
is  used  for  crushing  the  ore,  but  it  is  more  liable  to  get  out  of  order,  and 
is  not  so  easily  cleaned  as  the  mortar  and  pestle.  Fig.  2  shows  an  arrange- 
ment for  facilitating  the  final  grinding  in  the  agate  mortar,  in  which  the 
pestle  is  rotated  by  a  Stow  flexible  shaft. 


AGATE   MORTARS. 


FIG.  2. 


FIG.    3. 


14  APPARATUS  FOR    THE   PREPARATION  OF   THE   SAMPLES. 

The  apparatus  shown  in  Fig.  3,  designed  by  Mr.  Maunsel  White,  has 
been  in  use  several  years  at  the  chemical  laboratory  of  the  Bethlehem  Iron 
Company,  and  has  worked  very  satisfactorily.  The  power  is  applied  from 
an  overhead  countershaft  not  shown  in  the  cut.  The  lower  portion  of  the 
vertical  shaft  carries  two  horizontal  pulleys,  A  and  B ;  these  pulleys  are 
connected,  as  shown,  with  the  spindle  carrying  the  pestle  and  with  the 
circular  box  D,  in  which  the  mortar  is  securely  fastened  by  four  claw-bolts, 
which  may  be  seen  in  the  drawing. 

The  piece  D  is  made  with  a  spindle  which  extends  down  into  a  bearing 
in  the  supporting  piece  H.  The  piece  H,  which  may  be  called  a  lever,  is 
secured  to  the  frame  F  by  a  bolt  which  passes  through  it,  and  around  which 
it  can  be  turned  through  an  angle  sufficient  to  permit  of  the  easy  emptying 
of  the  mortar  without  displacing  the  belt.  A  groove  at  the  farther  end  of 
H,  as  shown,  carries  a  weighted  rod  which  supplies  the  pressure  of  the 
mortar  against  the  pestle.  The  weights  are  made  movable  so  that  the 
pressure  can  be  varied  for  special  cases. 

The  agate  pestle  is  secured  in  a  brass  spindle  with  a  grooved  collar  for 
carrying  the  belt ;  this  spindle  revolves  in  a  bored  socket  in  the  piece  E, 
and  is  secured  from  dropping  out  by  means  of  a  small  nut,  shown  at  the 
top  of  the  piece.  The  piece  E  is  connected  to  the  frame  F  by  a  circular 
bolt,  the  end  of  which  is  supplied  with  an  arm  for  rocking  the  piece  E ; 
this  obtains  by  fastening  the  bolt  with  dowel-pins  where  it  passes  through 
the  piece  E  while  free  to  move  in  the  frame  F.  The  pulley  C  is  run  from 
the  countershaft,  and  revolves  a  small  shaft  whose  end  carries  a  crank 
connected  by  a  short  rod  to  the  bolt-arm  of  the  piece  E,  and  supplies  the 
power  and  means  for  the  rocking  motion. 

It  will  now  be  seen  that  while  the  mortar  revolves,  the  pestle,  revolving 
more  rapidly,  sweeps  across  the  face  of  the  mortar  by  the  rocking  motion 
of  the  piece  E,  thus  constantly  changing  the  material  between  the  grinding 
surfaces. 

In  taking  samples  of  iron  or  steel,  a  perfectly  clean  dry  drill  should  be 
used,  and  the  utmost  care  taken  to  prevent  grease,  oil,  or  dirt  of  any  kind 
from  getting  in  the  sample.  With  bar-iron  or  steel  the  scale  on  the 
outside  of  the  piece  should  be  removed  as  carefully  as  possible,  the  first 


DRILLING-MA  CHINES. 


drillings    from   each    hole   thrown   away,   and    the    remainder  thoroughly 
mixed    and    placed    in    a    perfectly    clean    dry    bottle.       Fig.    4.  shows    a 


FIG.  4. 


convenient  form  of  drill-press  for  the  purpose.  A  half-inch  Morse  twist- 
drill  is  the  best  for  general  use.  In  taking  samples  of  pig-iron,  the  loose 
sand  should  be  carefully  removed  from  the  outside  of  the  pig  and  a  piece 
of  stout  paper  wrapped  around  it  to  prevent  the  sand  and  slag  from  the 
outside  getting  mixed  with  the  clean  drillings,  which  are  received  on  a 
piece  of  glazed  paper  turned  up  at  the  edges  (Fig.  4).  Drillings  from 
pig-iron  can  be  best  mixed  by  rubbing  them  up  in  a  small  porcelain  mortar. 
At  blast-furnaces,  to  save  the  trouble  of  breaking  pieces  from  the  pigs  the 
arrangement  shown  in  Fig.  5  is  very  convenient,  as  half  a  pig  can  be 
placed  in  the  press.  The 
framework  is  securely 
bolted  to  the  table  on 
which  the  press  stands, 
and  the  pig  is  secured  by 
means  of  the  iron  clamps. 
By  removing  the  pieces  of 
wood  under  the  pig  it  is 


FIG.  5. 


lowered    so    that    two    or 

three   holes  can  be  bored 

in  different  parts  of  the  face  of  the  pig  to  get  an  average.     By  taking  one 

pig  from  the  first  bed,  one  from  the  last,  and  one  from  an  intermediate  bed, 


i6 


APPARATUS  FOR    THE   PREPARATION  OF   THE   SAMPLES. 


a  good  average  of  each  cast  may  be  obtained.  When  the  ore  varies,  or 
when  mixtures  of  different  ores  are  used,  these  precautions  are  very 
necessary  to  get  a  sample  that  will  really  represent  an  average  of  the 
cast. 

Drillings  from  large  ingots  must  be  taken  by  means  of  an  ordinary  brace. 

Fig.  6  shows  an  apparatus  for  the  drilling  and  weighing  of  samples  of 
steel  for  colorimetric  carbon  or  other  rapid  determinations,  designed  by 


FIG.  6. 


Mr.  Maunsel  White,  and  in  use  at  the  laboratory  of  the  Bethlehem  Iron 
Company.  The  drill  is  mounted  above  the  balance,  the  point  of  the  drill 
directly  overhanging  the  balance-pan.  The  piece  to  be  drilled  is  placed 
against  the  semicircular  plate  carried  by  the  two  rods  that  pass  through 
the  drill-frame  ;  on  the  rear  end  of  each  rod  is  a  coiled  spring  which 
supplies  the  pressure  necessary  for  drilling.  The  rear  ends  of  the  rods  are 
held  together  by  a  tie-piece,  which  is  connected  to  a  lever  operated  by  the 


SPIEGEL    MORTAR. 


foot,  so  that  the  rods  and  plate  can  be  forced  forward  for  the  reception  of 
the  piece  to  be  drilled. 

The  balance  is  supplied  with  an  overhead  pan  which  receives  the  drill- 
ings guided  to  it  through  the  funnel  fixed  in  the  top  of  the  balance-case 
for  this  purpose.  When  the  pan  falls,  showing  that  sufficient  sample  has 
been  drilled,  pressure  is  applied  to  the  lever  by  the  foot  and  the  piece 
taken  out.  The  balance-case  rests  upon  an  iron  plate  grooved  on  the 
bottom  ;  these  grooves  engage  with  guides  screwed  to  the  table  and  permit 
the  balance-case  to  be  pulled  forward,  which  facilitates  the  cleaning  of  the 
funnel  from  all  clinging  particles.  This  operation  is  done  with  a  camel's- 
hair  brush  or  a  feather.  A  magnet  is  run  around  in  the  lower  pans  to 
guard  against  the  chance  of  falling  particles  interfering  with  the  accuracy 
of  the  weights.  The  upper  door  of  the  balance-case  is  then  lowered  into 
the  position  shown  in  Fig.  6,  which  gives  free  access  to  the  upper  pan 
containing  the  sample.  The  sample  is  now  accurately  weighed,  the  pan 
lifted  out,  and  the  drillings  transferred  to  the  test-tube. 

The  use  of  a  ^-inch  twist-drill  has  been  adopted  and  found  to  give 
good  results.  The  pans  and  fun- 
nel are  aluminum  and  the  bearings 
agate ;  the  beam  is  short,  5  ^  inches 
in  length,  in  consequence  of  which 
the  weighing  is  done  rapidly. 

In  taking  samples  of  spiegel  or 
of  white-iron,  small  clean  pieces  from 
a  number  of  pigs  should  be  taken 
and  powdered  in  a  hardened  steel 
mortar.  The  mortar  shown  in  the 
sketch  (Fig.  7)  is  forged  from  high 
carbon  steel,  hardened,  and  the  tem- 
per drawn  from  the  outside.  This 
makes  the  mortar  both  hard  and  tough.  The  sheet-iron  cover  prevents 
the  pieces  from  flying.  The  face  of  the  pestle  is  very  hard,  and  the 
handle  comparatively  soft,  so  that  it  will  not  break  when  struck  by  the 
hammer. 


FIG.  7. 


i8 


GENERAL    LABORATORY  APPARATUS. 


In  taking  samples  for  analysis,  when   the  method  used   requires  the 
sample  to  be  in  a  fine  state  of  subdivision,  the  very  fine  part  of  the  sample 


FIG.  8. 


should  never  be  separated  from  the  coarser  particles  by  a  sieve  or  screen, 
but  the  sample  should  be  mixed  thoroughly,  and  a  portion,  fine  and  coarse 
together,  taken  and  powdered,  so  that  all  may  pass  through  the  sieve. 


GENERAL   LABORATORY   APPARATUS. 
Hot  Plate  and  Air-Bath. 

Fig.  8  shows  a  very  convenient  form  of  hot  plate,  and  Fig.  9  an  air- 
bath.     This  air-bath   is   made   from  an  ordinary  cast-iron  sink,  which  is 


AIR-BA  TH. 


supported  on  fire-bricks.  The  top  is  of  asbestos  board,  with  a  piece  of 
sheet-iron  underneath  to  strengthen  it.  The  holes  are  large  enough  to 
take  the  largest-sized  beakers,  while  the  smaller  beakers  are  supported  by 
asbestos  rings.  An  ordinary  gas-regulator  or  governor,  which  supplies 


FIG.  9. 


the  gas  at  a  constant  pressure,  keeps  the  temperature  sufficiently  uniform. 
Evaporations  may  thus  be  effected  with  great  saving  of  time  and  with 
little  danger  of  loss  by  spirting.  The  products  of  combustion  of  the  gas 
are  carried  off  by  a  separate  flue,  and  the  sulphuric  acid  formed  does  not 
come  in  contact  with  the  solutions  in  the  baths. 


20 


GENERAL    LABORATORY  APPARATUS. 


FIG.    10. 


The  hot  plate  is  generally  used  instead  of  a  sand-bath,  the  surface  of 
the  iron  being  kept  clean  and  free  from  rust  by  an  occasional  coat  of 
stove-polish.  Evaporations  on  the  hot  plate  may  be  hastened  by  standing 
the  beaker  containing  the  solution  inside  another  beaker  with  the  bottom 
cut  off.  Beakers  may  readily  be  cut  in  this  way  by  starting  a  crack  and 

leading  it  around  with  a  red-hot  iron  or  glass 
rod.  For  evaporating  solutions  in  capsules  or 
dishes  a  beaker  cut  off  in  this  way  and  placed 
on  a  tripod  covered  with  wire  gauze,  as  shown 
in  Fig.  10,  may  be  used  with  great  advantage. 
The  capsule  is  supported  on  an  asbestos  ring, 
A,  the  bottom  being  about  J^  inch  (12  mm.) 
from  the  wire  gauze.  A  piece  of  thin  asbestos 
board,  B,  about  ^  inch  (18  mm.)  in  diameter, 
rests  on  the  gauze  and  covers  the  point  of  the 
flame  of  the  Bunsen  burner,  and,  by  throwing 
the  heat  more  on  the  sides  of  the  capsule,  tends 
to  prevent  spirting  when  the  solution  in  the  capsule  gets  thick  and 
pasty. 


Apparatus  for  Hastening-  Evaporations 

The  little  piece  of  apparatus  shown  in  Fig.  1 1  was  designed  by  Mr.  J.  E. 
Whitfield  and  is  most  useful  in  hastening  evaporations.  It  consists  of  a 
platinum  tube  T3^-  of  an  inch  in  diameter,  coiled  above  the  burner  to  present 
more  heating  surface,  through  which  passes  a  blast  of  air.  As  the 
platinum  tube  and  Bunsen  burner  are  both  supported  on  the  arm  of  the 
stand,  the  level  of  the  tube  may  be  made  to  accommodate  itself  to  a  cru- 
cible on  a  stand,  to  a  capsule  on  a  tripod  (Fig.  10),  or  to  a  beaker  on 
the  air-bath.  In  the  treatment  of  the  insoluble  residues,  from  ores  by 
hydrofluoric  and  sulphuric  acids  it  is  quite  invaluable,  as  it  not  only 
hastens  the  evaporation  but  prevents  loss  by  spirting. 

The  blast  of  hot  air  breaks  the  bubbles  on  the  surface  of  the  liquid, 
and  when  properly  directed  it  gives  the  liquid  a  rotary  motion  that  tends 


IGNITING   PRECIPITA  TES. 


21 


to  throw  onto  the  sides  of  the  crucible  any  particles  of  the  liquid  thrown 
up  by  the  bubbles.  The  amount  of  heat  that  can  be  applied  to  a  crucible 
under  these  circumstances,  without  causing  loss,  is  really  surprising.  It  is 
equally  useful  when  evaporating  solutions  in  beakers  on  the  air-bath  or 
hot  plate.  In  laboratories  where  a  blast  of  air  is  always  at  command,  the 
principle  may  be  applied  in  many  ways  for  hastening  evaporations. 


FIG.   ii. 


Even  a  cold  blast  of  air  from  a  drawn-out  glass  tube  directed  on  the 
surface  of  a  liquid  hastens  the  evaporation  very  materially. 


Igniting-  Precipitates. 

For  ignitions,  a  Bunsen  burner  with  a  ring  to  regulate  the  supply  of 
air,  provided  with  an  ordinary  glass  chimney,  as  shown  in  Fig.  12,  is  most 


22 


GENERAL    LABORATORY  APPARATUS. 


convenient.  By  shutting  off  the  air  entirely  a  very  low  heat  may  be 
obtained,  which  is  not  rendered  variable  by  air-currents,  and  the  heat  of 
the  full  flame  of  the  burner  is  increased  by  the  greater  draft  caused  by  the 
chimney  and  the  perfect  steadiness  of  the  flame.  By  using  a  small  platinum 
rod  or  wire  to  support  the  cover  of  the  crucible,  as  shown  in  Fig.  12,  a 
gentle  current  is  induced  in  the  crucible,  which,  while  it  greatly  facilitates 
burning  off  carbon,  is  not  sufficiently  strong  to  cause  loss  by  carrying  off 
even  the  lightest  ash.  The  crucible  may  also  be  inclined  on  its  side,  as  in 


FIG.   12. 


FIG.   13. 


FIG.   14. 


Fig.  13,  the  heat  in  this  case  being  applied  near  the  top  of  the  crucible. 
Fig.  14  shows  an  easy  method  of  fitting  a  chimney  to  a  Bunsen  burner  by 
means  of  a  cork  and  an  ordinary  Argand  chimney-holder.  When  a  higher 
temperature  than  that  obtainable  by  a  Bunsen  burner  is  required,  a  blast- 
lamp,  worked  by  a  foot-bellows,  by  a  water-blast,  or  by  a  small  blower, 
is  used. 

Tripods. 

The  most  convenient  arrangement  for  heating  liquids  in  beakers,  flasks, 
etc.,  is  the  iron  tripod  (Fig.  15).     It  consists  of  a  cast-iron  ring  with  three 


GASOLINE   AND   ALCOHOL    LAMPS. 

legs    of    heavy   iron    wire    ^   inch    (6    mm.)    in   diameter. 

covered   with    brass   wire    gauze,  40    meshes    to 

the    inch,    which    can    be    replaced     when    it    is 

burned  out,  but  which  lasts  a  long   time.     The 

vertical    height    of    the    tripod    is    about    7^ 

inches    (191     mm.).       A    very    convenient    form 

of  burner  is  the  Finkner  ratchet-burner,  as  the 

flame    can    be    raised    or   lowered    by  means   of 

the    ratchet    on   the    burner,   thus    avoiding    the 

necessity  of  reaching  back  over  the  table  to  the 

gas-cock.     As  the  air  and  gas  are  both  turned 

off  at  once,  there  is  less  danger  of  the  flame  blowing  out  when  it  is  turned 

very  low. 

Gasoline  and  Alcohol  Lamps. 

When  illuminating  gas  is  not  obtainable  for  heatrng  purposes,  recourse 
must  be  had  to  gasoline  or  alcohol.  If  a  gasoline  gas  machine  is  available 
it  furnishes  a  fair  substitute  for  ordinary  illuminating  gas,  but  special 
burners  must  be  used.  These  will  be  found  described  in  any  dealer's 
catalogue.  Sometimes,  however,  it  is  necessary  to  depend  on  gasoline 
alone  as  a  source  of  heat,  and  in  this  event  the  best  burner  for  general  use 
is  the  Dangler  lamp,  which  can  be  used  for  heating  solutions  and  also  for 
making  ignitions  and  for  fusions.  This  lamp  is  made  on  the  principle  of 
the  plumber's  torch  or  melting-pot. 

Alcohol  is  too  expensive  for  general  use  for  heating  purposes,  but  for 
fusions  for  the  determination  of  sulphur  its  use  is  advisable  on  account  of 
the  presence  of  sulphur  compounds  in  gas.  There  are  many  patterns  of 
alcohol  lamps,  among  others  Barthel's  lamp  of  the  form  shown  in  the  cut 
(Fig.  1 6)  may  be  mentioned. 

Muffles. 

Some  analysts  prefer  to  make  ignitions  in  a  muffle,  and  where  no 
gas  is  available  it  certainly  offers  many  advantages. 


24  GENERAL   LABORATORY  APPARATUS. 

Any  good  form  of  muffle  furnace  heated  by  gasoline,  coke,  or  coal 
may  be  used  for  this  purpose,  but  the  muffle  should  not  be  less  than  4  or  5 

FIG.  1 6. 


o 


inches  in  height.     The  waste  heat  may  be  used  for  a  hot  plate  or  an  air- 
bath. 

Filter-Pumps. 

The  use  of  filter-pumps  for  Bunsen's  method  of  rapid  filtration  is  now 
very  general,  and  greatly  facilitates  many  operations.  The  kind  of  pump 
is  usually  determined  by  the  water-supply.  With  a  good  pressure  of 
water,  the  most  convenient  form  of  pump  is  the  injector.  Fig.  17  shows 
the  Richards  injector  united  with  an  air-cylinder,  from  which  a  current  of 
air  sufficient  for  an  ordinary  blast-lamp  may  be  obtained.  When  the  pump 
is  used  for  filtering  strong  solutions  of  nitric  acid  a  glass  injector  may  be 
used,  and  the  water  allowed  to  flow  at  once  into  the  sink  or  waste-pipe. 
When  the  pressure  of  water  is  not  great  enough  for  an  injector  the  Bunsen 
pump  may  be  used,  the  vacuum  obtained  of  course  depending  on  the 
amount  of  fall.  A  tank  with  a  ball-cock  attachment  makes  this  form  of 
pump  most  convenient. 

An  ordinary  air-pump  may  also  be  used  for  many  purposes,  but  of 


BUNSEN'S  METHOD    OF  RAPID    FILTRATION.  2$ 

course  is  unsuitable  for  filtering  corrosive  liquids,  such  as  nitric  acid, 
unless  a  wash-bottle  containing  a  caustic  alkali  is  interposed  between  the 
flask  and  the  air-pump.  The  apparatus  shown  in  Fig.  18  will  give  a  very 

FIG.  17. 


good  idea  of  an  arrangement  which  is  very  convenient  when  a  water-supply 
is  not  available.  The  jug,  which  may  be  of  three  or  five  gallons'  capacity, 
serves  as  a  reservoir.  It  connects  directly  with  the  air-pump. 

Bunsen's  Method  of  Rapid  Filtration. 

This  method  is  too  widely  known  to  make  a  detailed  description 
necessary,  but  some  hints  in  regard  to  the  details  may  be  useful.  In  the 
first  place,  it  is  very  difficult  to  get  good  60°  funnels,  so  that  the  little 
perforated  cones  of  platinum  to  support  the  point  of  the  filter,  which  are 


26 


GENERAL    LABORATORY  APPARATUS. 


sold  by  chemical  dealers,  rarely  fit  the  funnel,  and  when  they  do  not  fit, 
the  filters  are  apt  to  tear.     The  small  funnel  of  platinum  foil,  as  recom- 


FIG.  i 8. 


mended  by  Bunsen,  can  be  made  to  fit  the  funnel  better,  but  the  edges 
sometimes  cut  the  filter.  A  small  funnel  of  parchment  pricked  full 
of  pin-holes,  and  of  the  size  and  shape  of  the  platinum- 
foil  funnel,  w.orks  very  well.  It  is  a  mistake  to  use  too 
great  a  pressure,  especially  at  first,  and  the  filter  should 
be  kept  full.  The  filtering- flask  should  always  be 
connected,  not  with  the  vacuum-pipe  directly,  but 
with  another  flask  fitted  with  a  little  Bunsen  valve, 
which  allows  the  air  to  pass  into  the  vacuum-pipe, 
but,  in  case  of  a  sudden  stoppage  in  the  pump,  pre- 
vents the  back  pressure  from  entering  the  filtering- 
flask  and  blowing  out  the  contents  of  the  funnel. 

Fig.  19  shows  an  arrangement  for  filtering  into  a 
beaker  instead  of  into  a  flask.  It  is  necessary  to  have  a  glass  cover  over 
the  beaker,  as  shown  in  the  sketch,  on  account  of  the  tendency  the  solu- 


GOOCH' S  METHOD    OF  RAPID   FILTRATION.  2/ 

tion  has  to  spatter,  particles  of  the  solution  being  carried  out  of  the  beaker 
in  the  current  of  air  flowing  into  the  vacuum-pipe. 

Gooch's  Method  of  Rapid  Filtration. 

The  pierced  crucible  and  cone,  with  asbestos  felt,  devised  by  Gooch,* 
are  almost  indispensable  to  the  iron  analyst  for  the  proper  and  rapid  exe- 
cution of  many  operations,  as  will  be  seen  by  the  frequent  references  to 
them  in  the  descriptions  of  the  methods  given  farther  on.  Fig.  20  shows 
the  crucible  and  cap,  and  Fig.  21  the  cone.  The  asbestos,  which  should 
be  of  a  soft,  silky,  flexible  fibre,  is  scraped  longitudinally  (not  cut)  to  a  fine, 
soft  down,  purified  by  boiling  in  strong  hydrochloric  acid,  and  washed 
thoroughly  on  the  cone.  It  may  be  dried  and  kept  in  a  bottle.  The 

FIG.  20.  FIG.  21.  FIG.  22. 


perforated  crucible  is  placed  in  one  end  of  a  piece  of  soft  rubber  tubing, 
the  other  end  of  which  is  stretched  over  the  top  of  a  funnel,  as  shown  in 
Figs.  20  and  22.  The  neck  of  the  funnel  passes  through  the  stopper  of  a 
vacuum-flask.  To  prepare  the  felt,  pour  a  little  of  the  prepared  asbestos 
suspended  in  water  into  the  crucible  and  attach  the  pump.  The  asbestos 
at  once  assumes  the  condition  of  a  firm,  compact  layer,  which  is  washed 
with  ease  under  the  pressure  of  the  pump.  After  washing  the  felt,  suck 
it  dry  on  the  pump,  remove  the  crucible,  detach  any  little  pieces  of 
fibre  that  may  be  on  the  outside  of  the  bottom  of  the  crucible,  slip  on 
the  little  cap,  dry,  ignite,  and  weigh.  Remove  the  cap,  place  the  crucible 
in  the  rubber  holder,  start  the  pump,  and  pour  the  liquid  and  precipitate 
to  be  filtered  into  the  crucible,  wash,  dry,  ignite,  if  required,  cool,  and 

*  Proceedings  Am.  Acad.  Arts  and  Sciences,  1878,  p.  342  ;  Chem.  News,  xxxvii.  181. 


28  GENERAL    LABORATORY  APPARATUS. 

weigh  as  before.  The  cone  is  fitted  to  a  funnel  by  means  of  a  rubber 
band  stretched  over  the  top  of  the  funnel.  The  pressure  of  the  pump 
pulls  the  cone  down  so  that  the  overlapping  part  of  the  band  forms  a  tight 
joint  between  the  cone  and  the  upper  part  of  the  funnel  (Fig.  23).  The 
felt  is  prepared  in  the  same  manner  as  in  the  crucible. 
Fill  the  cone  with  the  asbestos  suspended  in  water, 
start  the  pump,  press  down  the  cone  into  the  funnel, 
and,  if  necessary,  pour  in  more  of  the  asbestos, 
letting  it  run  all  around  from  the  upper  edge  of  the 
cone  so  as  to  fill  all  the  holes  and  make  a  firm,  co- 
hesive layer  all  over  the  inside  of  the  perforated 
portion  of  the  cone.  Wash  it  well  with  water  and 
suck  it  dry.  It  will  then  be  ready  for  use.  The  cone 
is  not  intended  for  use  when  the  precipitate  is  to  be  weighed,  but,  as  it 
presents  a  very  large  filtering  surface,  it  is  most  useful  for  such  precipitates 
as  manganese  dioxide  precipitated  by  Ford's  method,  etc.  In  this  case, 
when  the  precipitate  has  been  washed  and  sucked  dry,  by  removing  the 
cone  from  the  funnel  and  carefully  separating  the  felt  from  the  sides  of  the 
cone  with  a  little  piece  of  flattened  platinum  wire,  it  may  be  removed  from 
the  cone  with  the  precipitate  enclosed  in  it,  and  the  whole  mass  transferred 
to  a  beaker  or  flask  for  resolution.  The  cones  may  be  of  various  sizes ; 
for  ordinary  use,  a  cone  I  ^  inches  (45  mm.)  in  diameter  is  very  convenient. 
They  may  also  be  used  with  a  paper  filter.  In  both  the  crucibles  and  cones 
the  holes  should  be  very  small,  and  drilled  (not  punched)  as  closely 
together  as  possible. 

Counterpoised  Filters. 

The  Gooch  crucible  and  felt  are  most  useful  for  weighing  precipitates 
which  are  to  be  dried  and  not  ignited,  as  in  the  direct  weighing  of  the 
phospho-molybdate  of  ammonium.  When  they  are  not  available,  however, 
recourse  must  be  had  to  counterpoised  filters.  The  best  method  for 
preparing  and  using  them  is  as  follows.  Take  two  washed  filters  of  the 
same  size  and  about  the  same  thickness,  fold  them  as  if  about  to  fit  them 
in  funnels,  and,  by  cutting  from  the  upper  edge  of  the  heavier  of  the  two 
with  a  pair  of  scissors,  make  them  nearly  balance.  Place  them  between  a 


WASHING-BOTTLES.  29 

pair  of  watch-glasses,  as  shown  in  Fig.  24,  dry  them  at  100°  C,  and  allow 

them  to  cool  in  a  desiccator.     Place  one  in  each  pan  of  the  balance,  and, 

handling  them  with  a  pair  of  forceps,  clip  them  until  they  balance  exactly. 

Place  each  filter  in  a  funnel,  filter  the  precipitate  on  one  of  them,  pass  the 

clear  filtrate  (not  the  washings)  through  the  other, 

and  wash  them  both  in  the  same  manner.     Re-  FlG-  24- 

move   them   from   the   funnels,   turning   over   the 

top  edges  of  the  filter  containing  the  precipitate  to 

prevent  any  of  the  latter  from  falling  out,  place 

them  in  a  watch-glass,  dry  them  at  100°  C.  (or  at 

the  required    temperature,   whatever   it   may   be), 

cover  them  with  the  other  watch-glass,  cool  in  a  desiccator,  place  them  on 

opposite  pans  of  the  balance,  and  the  weight  added  to  the  pan  containing 

the  empty  filter,  to  make  them  balance,  is  the  weight  of  the  precipitate. 

Filter-Paper. 

All  filter-paper  contains  more  or  less  inorganic  matter,  which  remains, 
after  burning  the  paper,  as  a  white  or  brownish  ash.  The  Swedish  paper 
with  the  water-mark  J.  H.  Munktell  leaves  the  smallest  amount  of  ash, 
and  this  ash  contains  from  35  to  65  per  cent,  silica,  besides  ferric  oxide, 
alumina,  lime,  and  magnesia  in  varying  proportions. 

Schleicher  &  Schull  and  Baker  &  Adamson  prepare  very  pure 
filters  by  washing  them  with  hydrochloric  acid  and  hydrofluoric  acid,  and 
these  should  always  be  used  for  very  accurate  work.  The  commoner  kinds 
of  German  paper  contain  much  larger  amounts  of  inorganic  matter  than 
the  Swedish  paper,  which  consists  principally  of  calcium  carbonate,  but 
sometimes  contains  appreciable  amounts  of  phosphates. 

Washing-Bottles . 

Figs.  25,  26,  27,  and  28  represent  different  forms  of  washing-bottles. 
Fig.  25  shows  a  bottle  for  use  with  ether  or  acids.  The  stopper  is  of  glass. 
For  ordinary  use  that  represented  in  Fig.  26  is  the  best.  The  neck  is 
wrapped  with  thin  asbestos  board,  covered  with  a  piece  of  wash-leather  or 
chamois,  which  is  sewed  to  keep  it  from  slipping.  This  is  very  necessary 


GENERAL   LABORATORY  APPARATUS. 


when  hot  water  is  used.  A  piece  of  soft  rubber  tubing  at  A  is  more 
pleasant  for  the  mouth  than  the  glass,  and  after  compressing  the  air  in  the 
flask  the  tube  can  be  grasped  with  the  teeth,  thus  keeping  up  the  stream 
of  water  for  some  time  without  effort.  It  also  prevents  the  lips  from  being 

FIG.  26. 


FIG.  2v 


FIG.  28. 


scalded  when  using  very  hot  water.  Fig.  27  shows  a  movable  tip,  which 
allows  the  stream  of  water  to  be  directed  by  means  of  the  finger.  The 
form  of  flask  shown  in  Fig.  27  is  very  convenient  to  use  with  ammonia- 
water,  etc.  The  tube  a  is  closed  with  the  index  finger,  while  the  Bunsen 
valve  b  closing  as  soon  as  the  air  is  compressed  in  the  flask  prevents  the 
vapors  from  coming  back  into  the  mouth,  and  the  stream  of  liquid  is 
stopped  instantly  by  removing  the  finger  from  a.  Fig.  28  shows  the 
Berzelius  form,  which  is  sometimes  very  useful.  The  air  is  compressed  by 
blowing  into  the  bottle  through  the  jet,  and  by  quickly  inverting  the  bottle 
the  stream  of  liquid  is  forced  out  until  the  equilibrium  is  restored.  It 
requires  a  little  practice  to  use  this  form  of  bottle  easily,  but  when  the  art 
is  once  acquired  it  can  be  used  with  ammonia-water  as  well  as  pure  water, 
and  the  facility  with  which  it  can  be  removed  and  pointed  in  any  direction 
with  the  hand  makes  it  most  convenient  for  some  purposes. 

Removing"  Precipitates  from  Beakers. 

A  feather  trimmed  in  the  way  shown  in  Fig.  29  may  be  used  to  remove 
particles   of   adhering   precipitates   from   beakers,   evaporating-dishes,   etc. 


CAPS  FOR   REAGENT-BOTTLES. 


A  piece  of  soft  rubber  tubing  on  the  end  of  a  piece  of  glass  rod  or  sealed 
glass  tube  is  much  more  effective  and  convenient  in  most  cases.  It  is 
made  by  taking  a  short  length  of  rubber  tubing,  placing  a  little  pure 


FIG.  29. 


FIG.  30. 


FIG.  31. 


caoutchouc  dissolved  in  chloroform  or  naphtha  in  one  end,  squeezing  the 
sides  together  between  two  pieces  of  board  (Fig.  31),  and  allowing  it  to 
remain  for  at  least  twenty-four  hours.  It  may  then  be  trimmed  down  and 
placed  on  the  end  of  a  piece  of  glass  rod  or  on  the  end  of  a  piece  of  glass 
tubing  having  the  ends  fused  together  (Fig.  30).  This  little  instrument 
has  acquired  the  name  of  "  policeman." 

Measuring-Glasses. 

In  adding  reagents  to  a  sample  or  to  a  solution,  measured  amounts 
should  nearly  always  be  used,  and,  as  it  is  generally  well  under  all 
circumstances  to  avoid  adding  them  from  the  bottle  direct,  little  beakers  of 
the  form  shown  in  Fig.  32  are  very  useful.  They  can  be  graduated  and 
marked  by  covering  the  side  with  a  thin  coating  of  paraffine, 
measuring  in  water  from  a  burette,  marking  the  levels  and 
amounts  in  the  paraffine  with  a  sharp-pointed  instrument,  and 
etching  them  in  the  glass  by  filling  the  marks  with  hydrofluoric 
acid.  After  standing  a  few  minutes  the  hydrofluoric  acid  may 
be  washed  off  under  the  hydrant  and  the  paraffine  removed 
with  hot  water.  As  the  amounts  are  intended  to  be  only  approximate,  no 
great  degree  of  care  need  be  exercised  in  the  graduation. 

Caps  for  Reagent-Bottles. 

The  stoppers  and  lips  of  reagent-bottles  are  very  apt  to  become  covered 
with  ammonium  chloride,  dust,  etc.,  when  exposed  in  the  laboratory, 
and  especially  such  as  are  not  in  constant  use, — volumetric  solutions,  stock- 


FIG.  32. 


GENERAL   LAB  OR  A  TOR  Y  APPARA  TUS. 


FIG.  33. 


bottles,  etc.  It  is  well  to  keep  them  always  covered  with  caps,  which  may 
be  bought  from  the  dealers,  or  with  cracked  beakers,  which  answer  the 
purpose  nearly  as  well  in  most  cases. 

Rubber   Stoppers. 

Rubber  stoppers  are  now  generally  used  instead  of  cork.  Solid 
stoppers  should  always  be  purchased,  and  the  holes  cut  with  the  ordinary 
cork-borers.  This  is  readily  done  by  moistening  the  cork-borer  with 
water  or  alcohol.  A  little  practice  will  enable  any  one  to  do  this  with 

great  ease. 

Desiccators. 

Crucibles  should  always  be  cooled  before  weighing  in  desiccators. 
The  form  shown  in  Fig.  33  is  most  convenient. 
The  desiccator  should  contain  fused  calcium  chlo- 
ride. The  crucible  rests  on  a  small  triangle,  which 
may  be  made  of  copper  wire,  each  side  being 
covered  by  winding  a  thin  strip  of  platinum  foil 
around  it  to  prevent  the  crucible  from  coming 
in  contact  with  the  copper,  which  may  become 
more  or  less  corroded. 

PLATINUM   APPARATUS. 

Crucibles. 

The  shape  of  the  crucible  is  of  considerable  importance  as  regards  its 
wearing  properties.     Fig.   34  shows  the   best   form   for   general   use.     A 
crucible  \y2  inches  (38  mm.)  high,  i^g-  inches  (33^  mm.) 
wide  at  the  top,  with  a  capacity  of  20  c.c.,  and  weighing 
with    the    lid    about    25    grammes,   is    well    adapted    for 
weighing  the  usual   precipitates  found  in  the  course  of 
iron    analysis.     For   fusions    a    much    larger   crucible    is 
necessary:    one    i|f   inches   (46    mm.)   high,    i-j-f   inches 
(46  mm.)  wide  on  top,  with  a  capacity  of  55   c.c.,  and 
weighing  about  60  grammes,  will   be   found   convenient  and   serviceable. 
Pure  platinum  is  the  best  metal  for  crucibles.     The  iridium  alloy,  at  one 


FIG.  34. 


DISHES.  33 

time  so  popular,  has  not  been  found  to  wear  well.  It  is  stiffer  than  the 
pure  metal,  but  much  more  liable  to  crack.  The  endurance  of  a  crucible 
depends  very  much  upon  the  treatment  it  receives.  The  salts  of  easily 
reduced  metals  fusing  at  a  low  temperature,  such  as  lead,  tin,  bismuth, 
antimony,  etc.,  should  never  be  ignited  in  platinum ;  besides  these,  the 
phosphoric  acid  in  some  phosphates  is  occasionally  partly  reduced, 
rendering  the  platinum  very  brittle.  A  platinum  crucible  should  never  be 
bent  out  of  shape  when  it  can  be  avoided,  and  a  wooden  plug  exactly  the 
shape  of  the  crucible  (Fig.  35)  is  very  useful  to  straighten  it  on  when  it 

has    been    bent.       It   should   always    be    carefully    cleaned 

FIG.  35. 

before  use:  the  precipitate  last  ignited  should  be  dissolved 


in  acid  if  possible,  and  the  crucible  washed  out  with  water, 

dried,  ignited,  and  cooled  in  a  desiccator  before  weighing. 

A  precipitate  of  ferric  oxide  will  sometimes  stain  a  crucible 

very  badly ;    this   stain   may  be   removed  by  allowing  the 

crucible  to   stand   with   cold    hydrochloric  acid   for  twelve 

hours,  and  then  warming  it  for  a  short  time.     Stains  that 

are  not  removed  by  hydrochloric  acid  may  be  removed  by  fusing  potassium 

bisulphate  in  the  crucible,  or  by  fusing  sodium  carbonate  in  it,  dissolving 

in  water,  and  then  treating  the  crucible  with  hydrochloric  acid.     Whenever 

a  crucible  begins  to  look  dull  and  tarnished  it  should  be  cleaned  inside  and 

out  with  very  fine  sea-sand   (not  sharp  sand)  by  moistening  the  finger, 

dipping  it  in  the  sand,  and  rubbing  the  crucible  with  it.     This  method  of 

cleaning  decreases  the  weight  of  the  crucible  very  slightly,  the  sea-sand 

burnishing  without  cutting  the  crucible.     It  is  very  convenient  to  have  each 

crucible  and  its  cover  marked  with  a  number,  as  shown  in  Fig.  34. 

Dishes. 

Fig.  36  shows  a  very  convenient  form  of  dish  for  the  determination  of 
silicon  in  pig-iron,  silica  in  iron  ores,  etc.  It  is  3^  inches  (83  mm.)  in 
diameter  and  2^  inches  (57  mm.)  high.  Fig.  37  is  for  such  work  as  precipi- 
tation of  ferric  oxide,  etc.  It  is  5  inches  (127  mm.)  in  diameter  and  3T5¥ 
inches  (84  mm.)  high.  The  wire  which  is  fused  into  the  top  of  the  dish 

3 


34  GENERAL   LABORATORY  APPARATUS. 

makes  it  much  stiffer  than  it  would  otherwise  be,  and  consequently  it  may 
be  made  lighter  and  cheaper  than  would  be  possible  without  the  wire.    The 

wire  is  hammered  out  and   helps 
FIG.  37. 

to  form  the  lip.     A  platinum  stir- 

Fu;.  36.  T^^^^  ^  f^(      rmg-rod,  formed  from  a  piece  of 

seamless  tubing,  rounded  and 
fused  together  at  the  ends,  is  use- 
ful for  many  purposes.  It  may 
be  from  5^  to  7  inches  (140  to 
179  mm.)  long,  ^  inch  (6  mm.)  in  diameter,  weighing  from  7.5  to  n 
grammes. 

Spatula. 

Fig.  38  shows  a  very  convenient  and  useful  form  of  spatula.  The 
blade  which  is  made  of  the  platinum-iridium  alloy, 

'  is  fused  into  a  tube  of  the  same  alloy  which  forms 

the  handle.  The  weight  of  the  spatula  in  the 

sketch  is   14  grammes,  length  6^  inches  (165  mm.). 

Triangles  and  Tripods. 

The  triangles  for  supporting  the  crucibles  during  the  ignition  are  shown 
in  Figs.  12  and  13,  as  are  also  tripods  for  holding  the  lids,  etc.  These  are 
made  from  wire  about  y1^  inch  (1.6  mm.)  diameter,  the  ends  are  fused,  and 
the  wire,  where  it  is  twisted,  has  the  parts  in  contact  fused  together  almost 
to  the  inside  of  the  triangle,  which  makes  it  much  stiffer.  The  triangles 
should  be  attached  to  the  iron  rings  of  the  supports  with  a  few  turns  of 
fine  platinum  wire. 

Crucible-Tongs. 

Fig.  39  shows  the  best  form  of  crucible-tongs.  The  part  from  a  to  b  is 
of  platinum,  the  straight  part  from  a  to  c  fitting  over  the  end  of  the  iron. 
The  surfaces  at  df  are  in  contact  when  the  tongs  are  closed,  and  with  this 
portion  the  lid  can  be  handled,  and  the  crucible  is  clasped  by  the  curved 
ends,  which  hold  it  firmly  without  danger  of  bending  the  crucible.  They 
are  especially  useful  in  handling  a  crucible  containing  a  liquid  fusion. 
Another  form,  shown  in  Fig.  40,  is  generally  of  brass,  the  points  and  bend 


BALANCES. 


35 


being  lined  with  platinum.     A  small  pair  of  forceps  (Fig.  41)  is  useful  for 
taking  the  crucible  from  the  desiccator  and  placing  it  on  the  balance,  the 


FIG.  40. 


FIG.  39. 


FIG.  41. 


lid  of  the  crucible  being  slipped  a  little  to  one  side  to  allow  one  of  the 
points  of  the  forceps  to  go  inside  the  crucible. 

Balances. 

The  balance  is  one  of  the  most  important  things  in  the  equipment  of  a 
laboratory,  and  a  cheap  balance  is  nearly  always  a  very  poor  investment. 

FIG.  42. 


The  quality  of  balances  has  improved  greatly  in  the  last  few  years,  and  it 
is  now  possible  to  get  a  most  admirable  instrument  of  this  kind  at  a  com- 


GENERAL    LAB  OR  A  TOR  Y  APPARA  TUS. 


paratively  low  price.  Fig.  42  shows  a  balance  which  for  sensitiveness  and 
quickness  is  unsurpassed.  It  is  made  to  carry  up  to  200  grammes  in  each 
pan.  The  beam  is  of  aluminum,  as  are  also  the  pans.  The  stirrups  are 
of  nickel,  the  knife-edges  and  bearings  of  agate,  while  the  arrangement 
for  carrying  the  riders  (Fig.  43)  is  most  ingenious  and  effective.  It  is  of 
course  very  convenient  to  have  one  balance  for  weighing  crucibles,  etc., 
and  another  for  weighing  samples  for  analysis.  The  balance  for  the 
latter  purpose  may  be  much  smaller  than  the  balance  for  the  former, 

and    should    be    provided 

FlG-  43-  with    a    small    aluminum 

pan  with  a  spout  (Fig.  44), 
to  facilitate  the  transfer 
of  samples  to  flasks,  test- 
tubes,  etc.  The  pan  should 
have  a  counterpoise.  A 

FIG.  44. 


pair  of  small  forceps,  slightly  magnetized,  may  be  used  to  advantage  in 
getting  exact  weights  of  steel  drillings,  and  a  camel's-hair  brush  is 
necessary  to  detach  small  particles  of  ore,  etc.,  from  the  aluminum  pan 
or  balanced  watch-glasses. 


Factor  "Weights. 

The  use  of  factor  weights  is  in  many  cases  extremely  convenient,  as  it 
does  away  with  all  calculation,  and  is  to  that  extent  time-saving  and  valu- 
able in  avoiding  one  source  of  error.  Thus,  in  determining  carbon  by  com- 
bustion in  steel,  using  2.7273  grammes  of  the  steel,  o.i  milligramme  of 
carbonic  acid  is  equal  to  o.ooi  per  cent,  of  carbon  in  the  steel.  For  deter- 
mining silicon  in  pig-iron  the  ^  factor  weight,  or  1.1755  grammes,  is  very 


DISTILLED   WATER. 


37 


convenient.  When  the  weight  of  silica  is  multiplied  by  4,  one  milligramme 
is  equal  to  O.oi  per  cent,  of  silicon.  Or,  for  rapid  silicon  determinations, 
the  YO-  factor  weight,  0.4702  gramme,  is  used. 


REAQENTS. 


Distilled  Water. 

When  only  a  small  amount  of  distilled  water  is  needed,  a  tin-lined 
copper  still  and  condenser,  such  as  are  furnished  by  all  dealers,  may  be 
used,  but  where  there  is  a  supply  of  steam,  an  arrangement  like  that  shown 


FIG.  45. 


in  Fig.  45  will  be  found  most  useful.  A  is  a  tin-lined  copper  cylinder,  with 
a  dome-shaped  top,  E,  fitted  to  A  by  the  joint  shown  in  the  sketch,  which 
may  be  made  tight  by  paper  or  a  linen  rag.  Two  perforated  shelves,  a,  a, 
support  layers  of  clean  quartz-gravel  or  pieces  of  block-tin,  which  wash  the 


38  REAGENTS. 

steam  and  prevent  dirt  from  being  carried  over  mechanically.  The  steam 
enters  at  B,  and  the  water  condensed  in  the  cylinder  A  passes  off  through 
the  pipe  C.  The  washed  steam  passes  up  through  the  block-tin  pipe  G, 
and  is  condensed  in  the  worm-tub  F.  A  glass  worm  should  never  be  used, 
as  the  water  condensed  in  it  dissolves  notable  amounts  of  glass. 

ACIDS    AND    HALOGENS. 

Hydrochloric  Acid.    HC1.      Sp.  gr.  1.2. 

Chemically  pure  hydrochloric  acid  is  readily  obtained.  It  should  be 
free  from  chlorine,  sulphuric  and  sulphurous  acids,  arsenic,  and  fixed  salts. 
To  test  for  sulphuric  and  sulphurous  acids,  evaporate  100  c.c.  to  dryness 
with  a  little  pure  potassium  nitrate,  redissolve  in  water  with  a  few  drops 
of  hydrochloric  acid,  filter,  if  necessary,  and  add  barium  chloride.  To 
test  for  arsenic,  put  into  a  clean  dry  test-tube  a  few  centigrammes  of  pure 
stannous  chloride,  pour  in  carefully  6  or  8  c.c.  hydrochloric  acid,  and 
gradually  2  or  3  c.c.  pure  sulphuric  acid,  shaking  the  test-tube  gently.  If 
the  hydrochloric  acid  is  free  from  arsenic  the  solution  remains  clear  and 
colorless,  but  if  arsenic  is  present  the  solution  becomes  yellowish,  then 
brownish,  and  finally  metallic  arsenic  is  deposited.  The  test-tube  should 
be  gently  warmed  if  no  reaction  occurs  at  first.  To  test  for  chlorine,  pour 
some  of  the  acid  into  a  solution  of  potassium  iodide  containing  a  little 
starch  solution.  A  blue  coloration  indicates  chlorine  or  ferric  chloride. 
To  test  for  metallic  salts,  neutralize  about  100  c.c.  of  the  acid  with  ammonia 
and  add  ammonium  sulphide.  To  test  for  salts  of  the  alkalies,  evaporate 
about  100  c.c.  of  the  acid  to  dryness,  and  test  any  residue  which  may 
remain. 

Nitric  Acid.     HNO3.     Sp.  gr.  1.41. 

Nitric  acid  should  be  free  from  nitrous  acid,  the  presence  of  which  may 
be  known  by  the  yellowish  color  it  produces.  It  may  be  freed  from  this 
gas  by  passing  a  current  of  air  through  the  acid  until  it  becomes  colorless. 
To  test  for  hydrochloric  acid  or  chlorine,  dilute  largely  and  add  a  solution 


ACIDS  AND  HALOGENS. 


39 


of  silver  nitrate.  To  test  for  fixed  salts,  evaporate  about  100  c.c.  to  dryness. 
The  ordinary  acid  diluted  with  an  equal  volume  of  water  gives  the  acid  of 
1.2  sp.  gr.  used  to  dissolve  steel  for  the  color  carbon  test.  It  should  be 
carefully  tested  for  chlorine  and  hydrochloric  acid. 

Sulphuric  Acid.     H2SO4.     Sp.  gr.  1.84. 

Sulphuric  acid  should  be  colorless.  To  test  for  oxides  of  nitrogen, 
Warington  *  suggests  placing  about  two  pounds  of  the  acid  in  a  bottle, 
which  it  half  fills,  and  shaking  violently.  The  air  washes  the  gases  out  of 
the  acid,  and  the  presence  of  the  oxides  of  nitrogen  may  be  detected  by 
placing  in  the  mouth  of  the  bottle  a  piece  of  filter-paper  saturated  with 
potassium  iodide  and  starch  solution,  which  is  colored  blue  when  any  of 
these  oxides  are  present.  To  test  for  lead,  supersaturate  some  of  the  acid 
with  ammonia  and  add  ammonium  sulphide. 

Hydrofluoric  Acid.     HF1. 

The  use  of  ceresine  bottles,  suggested  by  Prof.  Edward  Hart,  of 
Lafayette  College,  has  made  it  quite  possible  to  obtain  pure  hydrofluoric 
acid,  but  the  crude  acid  may 
be  redistilled  into  platinum 
bottles  in  the  laboratory.  The 
crude  acid,  which  may  be  pur- 
chased from  glass  engravers 
and  etchers,  is  distilled  from  a 
platinum,  silver,  or  lead  still, 
as  shown  in  Fig.  46.  The 
head  of  the  still  and  con- 
densing-tube  is  of  platinum. 
The  condensing  tube  runs 
through  a  copper  box  filled 

with  ice,  and  a  platinum  bottle  receives  the  condensed  acid.  Where 
the  tube  comes  through  the  lower  part  of  the  box  it  is  secured  by  a 
rubber  stopper,  and  a  small  bit  of  paper  around  the  tube  prevents  any 


FIG.  46. 


*  Crookes's  Select  Methods,  2d  ed.,  p.  494. 


40  REAGENTS. 

condensed  moisture  on  the  outside  of  the  tube  from  running  into  the  bottle. 
Before  distilling  the  acid,  put  into  it  a  few  crystals  of  potassium  perman- 
ganate and  a  few  c.c.  of  sulphuric  acid.  The  redistilled  acid  should  leave 
no  residue  upon  evaporation. 

Acetic  Acid.     H,C2H3O2  -f  Aq.     Sp.  gr.  1.04. 

Acetic  acid  of  the  strength  given  above  is  the  best  for  use  in  iron 
analysis.  It  should  give  no  residue  on  evaporation,  and  no  precipitate 
upon  neutralization  with  ammonia  and  the  addition  of  ammonium  sulphide. 
It  should  be  free  from  phosphoric  acid.  To  test  it  for  phosphoric  acid, 
evaporate  100  c.c.  nearly  to  dryness,  add  a  little  magnesium  mixture  and  a 
large  excess  of  ammonia,  cool  in  ice-water,  and  stir  vigorously.  When 
phosphoric  acid  is  present,  a  precipitate  of  ammonium  magnesium 
phosphate  will  be  obtained. 

Citric  Acid.     H3,C6H5O7,H2O. 

Citric  acid  is  easily  obtained  in  a  state  of  purity  in  the  form  of  crystals 
having  the  above  composition.  It  should  be  kept  in  the  solid  condition, 
and  dissolved  as  needed.  It  is  soluble  in  ^  part  of  water  at  15°  C. 

Tartaric  Acid.     H2,C4H4O6. 

Tartaric  acid  is  also  easily  obtained  sufficiently  pure  for  use  in  iron 
analysis.  The  crystals  should  be  dissolved  only  as  needed.  The  only 
impurity  is  a  small  amount  of  lime.  It  is  soluble  in  j£  part  of  water  at 
15°  C 

Oxalic  Acid.     H2,C2O4. 

Oxalic  acid  crystallizes  from  its  aqueous  solution  as  H2,C2O4,2H2O, 
soluble  in  87  parts  of  water  at  15°  C.  It  loses  its  water  of  hydration  very 
easily  even  at  the  ordinary  temperature  in  dry  air,  and  very  quickly  at 
100°  C. 

Bromine.     Br. 

Bromine  is  easily  obtained  in  a  condition  sufficiently  pure  for  use  as  a 
reagent.  It  is  a  dark  brown,  extremely  corrosive  liquid,  of  sp.  gr.  2.97. 


ACIDS  AND   HALOGENS.  41 

It  is  soluble  in  about  30  parts  of  water  at  15°  C.  It  is  best  kept  in  a 
glass-stoppered  bottle  with  a  ground  cap.  As  the  aqueous  solution  is 
generally  used,  it  is  convenient  to  put  only  a  small  amount — say  20  or 
30  c.c. — in  the  bottle,  fill  the  bottle  nearly  full  of  cold  distilled  water, 
shake  it  up  well,  and  pour  ofT  the  saturated  solution  as  required.  There 
usually  remains  in  the  bottom  of  the  bottle  a  small  amount  of  impurity, 
which  is  insoluble  in  water. 

Iodine.     I. 

Iodine  is  a  metallic-looking  crystalline  solid,  of  sp.  gr.  4.95.  Re- 
sublimed  iodine  is  not  sufficiently  pure  for  use,  and  must  be  redistilled 
with  great  care,  unless  it  is  used  as  iodine  dissolved  in  iodide  of  iron, 
and  filtered.  To  distil  it,  place  about  J^  kilo,  in  a  large  glass  retort  of 
about  2  litres'  capacity  connected  with  an  adapter  about  18  inches 
(456  mm.)  long  and  3  inches  (75  mm.)  in  diameter  at  the  largest  part. 
The  heat  from  a  Bunsen  burner  turned  quite  low  will  cause  the  violet 
vapors  of  iodine  to  pass  rapidly  into  the  adapter,  where  they  will  condense 
without  any  means  being  taken  to  cool  it.  By  gently  wanning  the  out- 
side of  the  adapter  after  the  distillation  has  been  finished,  the  iodine  may 
readily  be  detached  in  large  masses  and  removed.  It  should  be  kept 
in  a  wide-mouth,  glass-stoppered  bottle. 

Chlorine.     Cl. 

Chlorine  is  a  yellowish  gas  about  two  and  one-half  times  heavier 
than  air.  It  is  sparingly  soluble  in  water.  When  required  it  must  be 
made.  The  details  are  given  under  "  Determination  of  Silicon  in  Iron 
and  Steel." 

Sulphurous  Acid.     H2SO3. 

To  make  sulphurous  acid  gas,  mix  powdered  charcoal  and  strong 
sulphuric  acid  until  a  thin  paste  is  formed,  heat  the  paste  in  a  flask, 
very  gently  at  first,  and  pass  the  gas  through  a  washing-bottle  containing 
a  little  water.  The  reaction  is  C  -f  2H2SO4=  CO2  +  2SO2  +  2H2O.  The 
tube  leading  from  the  flask  into  the  washing-bottle  should  have  a  bulb 
in  it  to  prevent  the  reflux  of  water  into  the  flask  in  case  of  sudden 


42  REAGENTS. 

cooling.  Clippings  of  sheet  copper,  or  copper  turnings,  may  be  used 
instead  of  charcoal,  and  are  generally  to  be  preferred.  The  best  pro- 
portion is  250  grammes  of  copper  to  500  C-C-  of  strong  sulphuric  acid. 
The  aqueous  solution  of  the  gas  is  made  by  passing  the  washed  gas  into 
distilled  water. 

A  very  neat  and  inexpensive  method  of  making  saturated  solutions 
of  sulphurous  acid  is  to  buy  the  small  cylinders  containing  about  20 
ounces  of  liquefied  gas  each.  One  of  these  cylinders  contains  enough 
gas  to  saturate  ten  litres  of  water.  They  are  closed  with  a  small  lead 
tube  fused  at  the  end.  Straighten  out  the  tube  as  far  as  possible,  cut 
off  the  fused  end  and  slip  a  piece  of  rubber  tubing,  connected  with  a 
washing-bottle,  over  it  and  allow  the  gas  to  flow  through.  The  gas,  SO2, 
has  a  specific  gravity  of  2.21  (air=  i).  I  c.c.  of  water  at  15°  C.  dissolves 
0.1353  gramme  of  SO2. 

Chromic  Acid.     CrO3. 

Chromic  anhydride  as  a  red  powder  or  in  the  form  of  scarlet  crystals 
is  easily  obtained  in  a  state  of  purity.  It  is  deliquescent,  and  dissolves 
in  a  small  quantity  of  water,  forming  a  dark  brownish-colored  liquid.  It 
may  be  made  by  pouring  I  volume  of  a  saturated  solution  of  potassium 
bichromate  into  I  y2  volumes  of  strong  sulphuric  acid,  stirring  constantly. 
The  liquid  on  cooling  deposits  needles  of  chromic  anhydride,  which  must 
be  separated  from  the  mother-liquid  and  purified  by  recrystallization. 

GASES. 

Carbon  Dioxide.     Carbonic  Acid  Gas.     CO2. 

The  best  form  of  generator  is  shown  in  Fig.  47.  It  was  first  suggested 
by  Casamajor.*  It  consists  of  a  large  tubulated  bottle,  the  bottom  of 
which  is  covered  to  the  depth  of  about  I  inch  (25  mm.)  with  buckshot,  on 
top  of  which  rest  lumps  of  marble.  Dilute  hydrochloric  acid  (i  acid  to  5 
water)  is  admitted  through  the  tube  which  enters  at  the  tubulure  at  the 
bottom  of  the  bottle,  bending  down  so  as  to  reach  the  bottom  of  the  bottle. 
The  wash-bottle  A  contains  water.  By  blowing  in  the  rubber  tube 

*  American  Chemist,  vi.  209. 


GASES.  43 

attached  to  the  acid-bottle  the  acid  passes  over  into  the  tubulated  bottle. 
When  the  stopcock  K  is  closed,  the  pressure  in  the  tubulated  bottle  forces 
the  acid  back  into  the  acid-bottle.  When  the  acid  becomes  exhausted  and 
remains  in  the  tubulated  bottle,  pour  a  little  strong  hydrochloric  acid  into 
the  acid-bottle  and  blow  it  over  into  the  tubulated  bottle.  The  generated 
gas  will  force  the  liquid  back  into  the  acid-bottle,  when  it  can  be  replaced 
by  fresh  acid.  A  slightly  different  form  is  shown  in  Fig.  50. 

Hydrogen  Sulphide  Gas.     H2S. 

The  same  form  of  apparatus  is  used  for  generating  hydrogen  sulphide. 
Ferrous  sulphide  is  substituted  for  marble,  but  hydrochloric  acid  is  used 
instead  of  sulphuric  acid,  as  is  generally  advised,  for  the  ferrous  sulphate 
formed  crystallizes  out  and  clogs  the  apparatus. 

Hydrogen.     H. 

The  same  form  of  apparatus  as  that  used  for  carbonic  acid  and  hydrogen 
sulphide  can  be  used  to  advantage  for  generating  hydrogen  gas.  Pieces  of 
zinc,  which  may  be  obtained  by  melting  the  zinc  and  pouring  it  in  a  sheet 
about  y^  inch  (6  mm.)  thick,  so  that  it  can  easily  be  broken,  are  to  be 
used,  and  not  granulated  zinc.  Hydrochloric  acid  is  better  than  sulphuric. 

Oxygen  Gas.     O. 

Oxygen  compressed  in  cylinders  can  be  obtained  from  most  dealers  in 
chemicals,  but  it  should  always  be  carefully  tested  before  being  used  for 
the  determination  of  carbon  in  steel  or  iron,  as  the  cylinders  are  sometimes 
filled  with  coal-gas,  and  a  cylinder  which  has  once  held  coal-gas  is  rarely 
free  from  hydrocarbons. 

The  gas  may  be  made  on  a  small  scale  in  the  laboratory  by  carefully 
mixing  in  a  porcelain  mortar  100  grammes  potassium  chlorate  and  5 
grammes  powdered  manganese  dioxide,  transferring  to  a  retort,  which  the 
mixture  should  not  more  than  half  fill,  and  heating  carefully  over  a  Bunsen 
burner.  The  evolved  gas  may  be  collected  in  a  gas-holder  or  in  an  india- 
rubber  bag.  The  latter  is  not  to  be  recommended  for  use  for  carbon 
determinations,  as  rubber  is  very  liable  to  give  off  hydrocarbons. 


44  REAGENTS. 

ALKALIES    AND    ALKALINE    SALTS. 

Ammonium  Hydroxide.     Ammonia.     NELjHO. 

The  solution  of  ammonia  gas  (NH3)  commonly  used  is  of  sp.  gr.  0.88, 
and  contains  about  30  to  35  per  cent,  of  ammonia.  It  should  be  kept  in 
glass-stoppered  bottles  and  in  a  cool  place,  as  the  gas  passes  off  very 
rapidly  even  at  the  ordinary  temperature  when  open  to  the  air.  It  should 
be  colorless,  leave  no  residue  upon  evaporation,  be  free  from  chlorides 
and  sulphates,  and  give  no  precipitate  with  hydrogen  sulphide. 


Ammonium  Bisulphite. 
Ammonium  bisulphite  is  made  by  passing  sulphurous  acid  gas  into 
strong  ammonia  until  the  solution  becomes  yellowish  in  color  and  smells 
strongly  of  sulphurous  acid.  By  the  first  method  of  manufacture  of 
sulphurous  acid  given  on  page  41,  a  large  amount  of  carbonic  acid  is 
formed  at  the  same  time,  which  is  absorbed  by  the  ammonia.  This  is 
gradually  displaced  by  the  sulphurous  acid,  and,  if  the  solution  is  kept  cool, 
white  crystals  of  the  neutral  sulphite,  (NH4)2SO3H2O,  are  deposited.  These 
are  gradually  dissolved  by  the  excess  of  sulphurous  acid  until  the  solution 
becomes  quite  clear,  assuming  a  yellowish  tint.  When  copper  is  used 
instead  of  charcoal,  no  carbonic  acid  is  evolved  and  no  ammonium  carbon- 
ate is  formed.  The  cylinders  of  liquefied  gas  mentioned  on  page  42  may 
be  used  for  this  purpose.  One  cylinder  will  saturate  about  one  litre  of 
strong  ammonia.  By  exposure  to  air  ammonium  bisulphite  is  gradually 
oxidized  to  sulphate.  Old  ammonium  bisulphite  always  contains  a  small 
amount  of  hyposulphite,  which  occasions  a  precipitate  of  sulphur  when 
deoxidizing  solutions  of  ferric  salts.  It  is  not  now  difficult  to  purchase 
pure  ammonium  bisulphite,  but  sodium  bisulphite  is  very  apt  to  contain 
phosphoric  acid.  When  made  from  strong  ammonia-water,  18  c.c.  of 
bisulphite  will  deoxidize  a  solution  of  10  grammes  of  iron  or  steel. 

Ammonium  Sulphydrate.     Ammonium   Sulphide.     (NH4)2S. 
Ammonium  sulphide  is  made  by  saturating  strong  ammonia  with  hydro- 
gen sulphide  and  'adding  an  equal  volume  of  ammonia.     The  reactions  are 


ALKALIES  AND   ALKALINE   SALTS.  45 

NH4HO  +  H2S  =  NH4HS  -f-  H2O  and 
NH4HS  -f  NH.HO  ==  (NH4)2S  +  H2O. 
The  solution  becomes  yellow  by  age  or  by  exposure  to  the  air. 

Ammonium  Chloride.     NH^Cl. 

Ammonium  chloride  is  a  white,  crystalline,  anhydrous  salt,  soluble  in 
about  its  own  weight  of  water  at  100°  C.,  and  in  2.7  parts  of  water  at  18° 
C.  It  volatilizes  when  heated  without  previous  fusion.  The  salt  is  usually 
purified  by  sublimation.  It  generally  contains  a  little  iron,  but  is  free  from 
other  impurities.  To  prepare  ammonium  chloride  for  use  in  J.  Lawrence 
Smith's  method  for  decomposition  of  silicates,  dissolve  it  in  boiling  water 
and  evaporate  down  on  a  water-bath  or  air-bath.  When  the  salt  begins 
to  crystallize  out,  stir  vigorously.  The  crystals  formed  will  be  very  small. 
Drain  off  the  liquid  and  dry.  The  salt  can  then  readily  be  powdered. 

Ammonium  Nitrate.     NH^NOg. 

Ammonium  nitrate  is  a  white,  crystalline  salt,  soluble  in  one-half  its 
weight  of  water  at  1 8°  C,  and  in  much  less  at  100°  C.  When  dissolved 
in  water  it  produces  great  cold.  By  evaporation  it  loses  ammonia  and 
becomes  acid.  When  heated  it  fuses  at  108°  C.,  and  is  decomposed 
between  230°  C.  and  250°  C.  into  water  and  nitrous  oxide,  NH4NO3  = 
2H2O  -f-  N2O.  It  should  leave  no  residue  when  volatilized. 

Ammonium  Fluoride.     NH4F1. 

Ammonium  fluoride  may  be  made  by  saturating  hydrofluoric  acid 
by  ammonia.  The  salt  crystallizes  when  left  to  evaporate  over  quicklime. 
It  is  slightly  deliquescent,  and  therefore  difficult  to  keep,  as  the  solution 
attacks  glass. 

Ammonium  Acetate.     NH4C2H3O2. 

Ammonium  acetate  is  best  made  by  slightly  acidulating  ammonia  by 
acetic  acid.  One  volume  of  strong  ammonia-water  requires  about  2 
volumes  of  acetic  acid,  1.04  sp.  gr.,  to  neutralize  it.  It  is  best  to  make 
it  as  needed,  as  it  decomposes  when  kept. 


46  REAGENTS. 

Ammonium  Oxalate.      (NH4)2C2O4  -f  H2O. 

Ammonium  oxalate  is  a  white  salt,  crystallizing  in  long  prisms  united 
in  tufts.  It  is  soluble  in  20  parts  of  water  at  18°  C. 

Sodium  Hydroxide.     Caustic  Soda.      NaHO. 

Fused  sodium  hydroxide  purified  by  alcohol  is  sufficiently  pure  for 
ordinary  purposes.  It  forms  white  opaque  masses,  having  a  strong  affinity 
for  water.  It  dissolves  in  water  with  evolution  of  heat.  Pure  sodium 
hydroxide  is  prepared  by  allowing  metallic  sodium  to  decompose  water 
in  a  platinum  dish.  It  must  be  kept  in  a  silver  or  platinum  bottle,  as  the 
solution  acts  very  rapidly  on  glass. 

Sodium- Ammonium  Phosphate.    Microcosmic  Salt.    NaNH4HPO4,4H2O. 

Sodium-ammonium  phosphate  (microcosmic  salt)  is  a  white,  crystalline 
salt,  soluble  in  6  parts  of  cold  and  I  part  of  hot  water.  It  should  not  be 
kept  in  solution  for  any  great  length  of  time,  as  it  attacks  glass  very 
readily.  It  loses  its  water  of  crystallization  very  easily,  and  when  heated 
gives  off  its  ammonia,  leaving  pure  sodium  metaphosphate,  which  in  the 
fused  condition  dissolves  metallic  oxides  in  many  cases  with  the  production 
of  characteristic  colors,  which  makes  it  a  valuable  reagent  for  blow-pipe 
analysis.  It  is  easily  obtained  in  a  state  of  purity. 

Sodium  Carbonate.     Na2CO8. 

Sodium  carbonate  is  never  quite  pure.  It  always  contains  small 
amounts  of  silica,  alumina,  lime,  and  magnesia,  besides  sulphuric  acid. 
It  may  generally  be  obtained  quite  free  from  phosphoric  acid.  Every 
lot  should  be  carefully  examined  for  all  the  above  impurities,  and  the 
amount  per  gramme  noted,  so  that  the  proper  subtraction  may  be  made 
in  each  analysis.  It  is  used  in  solution  only  for  the  neutralization  of 
solutions,  as  in  the  determination  of  manganese  by  the  acetate  method, 
and,  as  the  solution  attacks  glass  very  rapidly,  it  is  best  to  dissolve  the 
salt  only  as  it  is  needed. 


ALKALINE   SALTS.  47 

Sodium  Nitrate.     NaNO3. 

Sodium  nitrate  is  used  occasionally  instead  of  potassium  nitrate  in 
making  fusions  of  ores  containing  titanic  acid.  It  may  be  prepared  by 
acidulating  a  strong  solution  of  sodium  carbonate  with  nitric  acid, 
heating  until  the  water  and  excess  of  nitric  acid  are  driven  off,  and 
powdering  the  dry  salt. 

Sodium  Hyposulphite.     Sodium  Thiosulphate.     Na2S2O3  -f-  5H2O. 

Sodium  hyposulphite  is  very  soluble  in  water,  but  decomposes  even 
in  tightly  stoppered  bottles,  sodium  sulphate  being  formed  and  sulphur 
precipitated.  It  should,  therefore,  be  dissolved  only  as  used. 

Sodium  Acetate.     NaC2H3O2  -f  3H2O. 

Crystallized  sodium  acetate  dissolves  in  3.9  parts  of  water  at  6°  C. 
It  is  rarely  quite  pure,  containing,  usually,  calcium  and  iron  salts,  but  it 
may  be  used  after  solution  and  filtration  for  partial  analyses,  as  in  the 
determination  of  manganese  by  the  acetate  method,  etc.  In  complete 
analyses  it  is  better  to  use  ammonium  acetate.  When  the  use  of  sodium 
acetate  is  unavoidable,  it  can  be  made  by  dissolving  C.  P.  sodium  car- 
bonate in  acetic  acid,  boiling  off  the  liberated  carbonic  acid,  and  adding' 
acetic  acid  to  slight  acid  reaction. 

Potassium  Hydroxide.  Caustic  Potash.  KHO. 
Potassium  hydroxide  purified  by  solution  in  alcohol,  filtration,  and 
subsequent  evaporation  to  dryness  and  fusion,  is  quite  pure  enough  for  all 
the  ordinary  purposes  of  iron  analysis.  An  aqueous  solution  of  1.27 
sp.  gr.  is  used  to  absorb  carbonic  acid  in  the  determination  of  carbon  in 
iron  and  steel,  in  the  determination  of  carbonic  acid  in  ores,  etc. 
300  grammes  of  fused  potassium  hydroxide  dissolved  in  I  litre  of 
water  will  give  a  solution  of  about  this  strength. 

Potassium  Nitrite.     KNO2. 

Potassium  nitrite  is  used  to  separate  nickel  and  cobalt.  It  is  difficult 
to  buy  the  pure  salt,  but  it  is  easily  made  as  follows.  Heat  I  part  of 


48  REAGENTS. 

potassium  nitrate  in  an  iron  dish  until  it  is  just  fused,  then  add,  with 
constant  stirring,  2  parts  of  metallic  lead.  Raise  the  heat  slightly  to 
complete  the  oxidation  of  the  lead,  and  allow  the  mass  to  cool.  Treat 
the  mass  with  water,  filter  from  the  lead  oxide,  pass  carbon  dioxide 
through  the  solution  to  precipitate  the  greater  part  of  the  dissolved  lead 
oxide,  and  filter.  To  the  filtrate  add  a  little  ammonium  sulphide  to  pre- 
cipitate the  last  traces  of  lead,  filter,  evaporate  to  dryness,  and  fuse  in  a 
platinum  dish  to  decompose  any  hyposulphite  that  may  have  been  formed, 
and  preserve  the  fused  salt  for  use.  Potassium  nitrite  is  deliquescent. 

Potassium  Nitrate.     KNO3. 

Potassium  nitrate  is  a  white,  crystalline  salt,  anhydrous,  and  soluble 
in  jy2  parts  of  water  at  o°  C.,  and  in  0.4  part  of  water  at  100°  C.  It 
melts  below  a  red  heat  to  a  colorless  liquid,  and  at  a  red  heat  gives  off 
oxygen  gas  more  or  less  contaminated  by  nitrogen,  being  converted  into 
potassium  nitrite  and  potassium  oxide.  The  salt  may  be  purchased  in  a 
sufficient  state  of  purity  for  all  purposes  of  iron  analysis,  but,  as  it  may 
contain  small  amounts  of  sulphuric  acid,  the  amount  should  always  be 
determined  and  the  proper  allowance  made  when  it  is  to  be  used  for  the 
estimation  of  sulphur  in  ores. 

Potassium  Sulphide.     K2S. 

Potassium  sulphide  is  made  by  passing  hydrogen  sulphide  into  a 
solution  of  caustic  potash  and  filtering  from  any  precipitated  alumina  or 
ferrous  sulphide.  It  is  used  instead  of  the  corresponding  ammonia-salt 
when  the  solution  contains  copper,  as  copper  sulphide  is  slightly  soluble 
in  ammonium  sulphide. 

Potassium  Bichromate,     K2Cr2O7. 

Potassium  bichromate  is  an  orange-colored,  anhydrous,  crystalline 
salt,  soluble  in  20  parts  of  water  at  o°  C,  and  in  I  part  of  water  at 
100°  C.  It  melts  below  a  red  heat  to  a  transparent  red  liquid,  crumbling 
to  powder  upon  cooling.  Heated  with  strong  sulphuric  acid  it  gives  off" 


POTASSIUM  SALTS.  49 

about  one-sixth  its  weight  of  oxygen  gas,  the  reaction  being  K2Cr2O7  + 
4H2SO,=  Cr2K2(SO4)4  +  4H2O  +  30.  It  is  readily  obtained  in  a  state  of 
purity,  but  should  always  be  fused  to  destroy  any  organic  matter  before 
being  used  to  determine  carbon  in  iron  or  in  ores. 

Potassium   Chlorate.     KC1O3. 

Potassium  chlorate  is  a  white,  crystalline,  anhydrous  salt.  It  is  soluble 
in  about  30  parts  of  water  at  o°  C.,  and  in  about  2  parts  at  100°  C.  It 
is  readily  decomposed  by  heat,  first  into  a  mixture  of  potassium  chloride 
and  perchlorate,  a  portion  of  the  oxygen  being  set  free,  and  at  a  higher 
temperature  the  perchlorate  is  decomposed,  the  remaining  oxygen  is  given 
off  and  potassium  chloride  alone  remains.  It  is  easily  obtained  in  a 
sufficient  state  of  purity  for  use  in  iron  analysis.  Heated  with  nitric  acid 
it  yields  potassium  nitrate  and  perchlorate,  water,  chlorine,  and  oxygen, 
thus : 

8KC1O3  +  6HNO3  =  6KNO3  +  2KC1O4  +  6C1  -f  1 30  +  3  H2O. 

Heated  with  hydrochloric  acid  it  gives  potassium  chloride,  water,  and  a 
mixture  of  chlorine  peroxide  and  chlorine,  called  euchlorine,  thus  : 

4KC1O3  -J-  1 2HC1  =  4KC1  +  6H2O  +  3C1O2  +  9C1. 

Potassium  Bisulphate.     KHSO4. 

Potassium  bisulphate  is  a  white,  crystalline  salt,  soluble  in  about  one- 
half  its  weight  of  boiling  water.  A  large  amount  of  water  decomposes  it 
into  potassium  sulphate  and  free  sulphuric  acid  ;  even  in  the  presence  of 
a  large  excess  of  sulphuric  acid  the  neutral  salt  crystallizes  out,  leaving 
free  sulphuric  acid  in  the  solution.  Potassium  bisulphate  melts  at  197°  C. ; 
at  higher  temperatures  it  gives  off  water,  leaving  the  anhydrous  salt,  and 
at  a  red  heat  it  gives  off  sulphuric  acid,  leaving  the  neutral  sulphate.  It 
is  difficult  to  obtain  it  very  pure,  but  it  may  be  made  as  follows.  Dissolve 
potassium  bicarbonate  in  water,  filter,  and  from  a  graduated  vessel  add 
sulphuric  acid  until,  after  boiling  off  the  liberated  carbonic  acid,  the 
solution  is  neutral,  or  but  very  faintly  alkaline  to  test-paper.  Filter,  if 
necessary,  and  to  the  filtrate  add  as  much  sulphuric  acid  as  was  added 

4 


50  REAGENTS. 

in  the  first  place  to  neutralize  the  bicarbonate.  Boil  the  solution  down, 

and    finally  fuse  the  mass  in   a  platinum  dish.  Cool   it,  and  when  it  is 

almost   ready  to  solidify  pour    it    into  another  dish.     Break    it    up,   and 
preserve  it  in  glass-stoppered  bottles. 

Potassium  Iodide.     KI. 

Potassium  iodide  is  a  white,  crystalline,  anhydrous  salt,  very  soluble 
in  water,  and  in  dissolving  it  causes  a  fall  of  temperature  in  the  solution. 
It  is  soluble  in  about  0.8  part  of  water  at  o°  C,  and  in  0.5  part  of  water 
at  100°  C.  It  is  soluble  in  6  parts  of  alcohol  at  the  ordinary  temperature, 
and,  when  dissolved,  if  the  addition  of  hydrochloric  acid  does  not  turn  it 
brown,  it  is  free  from  iodate.  A  solution  of  I  part  of  potassium  iodide  in 
2  parts  of  water  will  dissolve  2  parts  of  iodine,  but  upon  dilution  some 
of  the  iodine  is  precipitated. 

Potassium  Permanganate  .     KMno4  (or  K2Mn2O8). 

Potassium  permanganate  is  a  dark  purple-red,  anhydrous  salt,  crystal- 
lizing in  long  needles.  It  is  soluble  in  16  parts  of  water  at  15°  C.  It  is 
easily  obtained  very  pure,  but  the  solution  should  always  be  filtered 
through  ignited  asbestos,  as  paper  has  a  strong  reducing  action  on  it. 


Potassium  Ferrocyanide.     ~K^Fe2CyQ  -f-  3H2O. 

Potassium  ferrocyanide  is  a  yellow,  crystalline  salt,  soluble  in  4  parts 
of  water  at  o°  C.,  and  in  »2  parts  of  water  at  100°  C.  It  is  used  as  a 
reagent  to  show  the  presence  of  ferric  salts,  which  produce  a  blue  color- 
ation, caused  by  the  formation  of  ferric  ferrocyanide  (Prussian  blue). 

Potassium  Ferricyanide.     K3Fe2Cye. 

Potassium  ferricyanide  is  a  blood-red,  anhydrous,  crystalline  salt, 
soluble  in  about  3.1  parts  of  water  at  o°  C.,  and  in  1.3  parts  of  water  at 
100°  C.  The  dilute  solution,  like  that  of  the  ferrocyanide,  is  yellow  in 
color.  Ferrous  salts  added  to  the  solution  give  a  blue  coloration,  due  to 
the  formation  of  ferrous  ferricyanide,  while  ferric  salts  produce  no  change 
of  color.  The  ferricyanide  should  never  be  kept  in  solution. 


SALTS    OF  ALKALINE   EARTHS.  51 

SALTS  OF  ALKALINE  EARTHS. 

Barium  Carbonate.     BaCO3. 

Barium  carbonate  prepared  by  precipitation  is  a  soft  white  powder. 
It  is  difficult  to  obtain  in  a  state  of  purity,  but  it  is  easily  prepared  by 
adding  a  solution  of  ammonium  carbonate  to  a  clear  boiling-  solution  of 
barium  chloride,  and  washing  the  precipitated  barium  carbonate  with  hot 
water,  first  by  decantation  and  afterwards  on  a  filter.  The  ammonium  car- 
bonate should,  of  course,  be  free  from  sulphate.  The  thoroughly  washed 
barium  carbonate  should  be  transferred  to  a  bottle  and  shaken  up  with 
water,  in  which  condition  it  is  ready  for  use.  Barium  carbonate  is  very 
slightly  soluble  in  water,  requiring,  according  to  the  different  authorities, 
from  4,000  to  25,000  parts  of  water  to  dissolve  it.  It  is  poisonous.  • 


Barium  Acetate. 

Barium  acetate  may  be  prepared  by  dissolving  pure  barium  carbonate 
in  acetic  acid.  It  crystallizes  with  I  or  3  molecules  of  water,  but  dried  at 
O°  C,  or  exposed  to  the  air,  it  effloresces  and  yields  the  anhydrous  salt 
as  a  white  powder.  It  is  very  soluble  in  water,  dissolving  in  about  2  parts 
of  water  at  O°  C.,  and  in  about  I  part  at  100°  C.  When  heated  it  decom- 
poses into  acetone  and  barium  carbonate,  thus  : 

0     =  CH0  +  BaCO. 


Barium  Chloride.     BaCl2,2H2O. 

Barium  chloride  is  a  white,  crystalline  salt,  soluble  in  about  3  parts 
of  water  at  15°  C.,  and  in  about  \y2  parts  at  100°  C.  Heated  to  100°  C. 
it  loses  its  water  of  crystallization,  yielding  the  anhydride  as  a  white 
mass,  which  melts  at  a  full  red  heat  Barium  chloride  is  almost  insoluble 
in  strong  hydrochloric  acid.  It  is  used  almost  exclusively  for  the  deter- 
mination of  sulphuric  acid,  and  may  be  kept  in  solution  for  this  purpose. 
IOO  grammes  of  the  crystallized  salt  dissolved  in  i  litre  of  water  is  a  good 
proportion  to  use.  Of  this  solution  10  c.c.  will  precipitate  1.16  grammes 
of  barium  sulphate,  equal  to  0.4  gramme  sulphuric  anhydride  or  0.16 
gramme  sulphur. 


52  REAGENTS. 

Caustic  Baryta.     Barium  Hydroxide.     BaH2O2,8H2O. 

Barium  hydroxide  is  a  white,  crystalline  salt,  soluble  in  20  parts  of 
water  at  15°  C,  and  in  3  parts  of  water  at  100°  C.  The  anhydride  may 
be  prepared  by  heating  barium  nitrate  to  redness  in  a  platinum  crucible, 
raising  the  heat  gradually  at  first  to  avoid  loss  from  frothing.  It  attacks 
platinum,  however,  at  a  high  temperature.  The  solution  has  a  strong 
affinity  for  carbonic  acid,  absorbing  it  readily  from  the  air,  the  barium 
carbonate  so  formed  causing  a  scum  on  the  surface  of  the  solution.  The 
solution  attacks  glass  very  strongly. 


Calcium  Chloride.     CaCl2. 

Crystallized  calcium  chloride  loses  all  its  water  of  crystallization  at 
200°  C.,  yielding  the  white  porous  anhydrous  chloride,  which  is  very 
deliquescent.  The  anhydrous  salt  fuses  at  a  low  red  heat,  but  is  partly 
changed  to  oxide.  For  this  reason  the  fused  salt  should  never  be  used 
for  drying  carbonic  acid  gas  in  the  determination  of  this  gas,  as  some 
of  it  is  taken  up  by  the  calcium  oxide.  A  solution  of  calcium  chloride 
containing  59  parts  of  the  anhydrous  salt  to  100  parts  of  water  boils  at 
115°  C,  a  saturated  solution  at  179.5°  C. 


Calcium  Carbonate.     CaCO3. 

Pure  calcium  carbonate,  for  use  in  Prof.  J.  Lawrence  Smith's  method 
for  the  determination  of  alkalies  in  silicates,  is  prepared  as  follows. 
Dissolve  marble  or  calcite,  free  from  magnesia,  in  dilute  hydrochloric 
acid,  add  an  excess  of  powdered  marble,  heat  the  solution,  and  add 
some  milk  of  lime  to  precipitate  magnesia,  calcium  phosphate,  etc. 
Filter,  heat  the  solution  almost  to  boiling,  and  precipitate  by  ammonium 
carbonate.  The  calcium  carbonate  formed  is  a  very  dense  powder,  which 
settles  readily  and  is  easily  washed.  Wash  thoroughly,  dry,  and  preserve 
for  use. 


METALS  AND   METALLIC  SALTS.  53 

METALS    AND    METALLIC    SALTS. 

Metallic  Copper. 

Metallic  copper  absorbs  chlorine  gas  at  ordinary  temperatures,  and 
is  used  in  iron  analysis  to  absorb  any  chlorine  that  may  be  given  off 
during  the  combustion  of  the  carbonaceous  matter  liberated  by  the 
action  of  solvents  on  iron  and  steel.  It  is  used  in  the  form  of  drillings, 
which  should  be  taken  with  a  perfectly  dry  drill,  and  which  should  be 
free  from  oil  and  grease.  The  drillings  should  be  kept  in  a  stoppered 
bottle,  and  may  be  used  as  long  as  they  are  perfectly  bright  and  clean. 

Cupric  Sulphate.      CuSO4,5H2O. 

Cupric  sulphate  is  a  blue,  crystalline  salt,  soluble  in  2.7  parts  of  water 
at  1 8°  C,  and  in  0.55  part  of  water  at  100°  C.  The  aqueous  solution 
of  the  neutral  salt  is  strongly  acid  to  litmus- paper.  The  crystals  of  cupric 
sulphate  effloresce  on  the  surface  when  exposed  to  the  air;  heated  to 
IOO°  C.  they  lose  4  molecules  of  water,  and  when  heated  to  200°  C. 
they  lose  the  remaining  molecule.  The  anhydrous  salt  is  a  white  saline 
mass,  which  is  decomposed  at  a  bright  red  heat,  giving  off  sulphurous 
acid  and  oxygen  and  leaving  cupric  oxide.  The  anhydrous  salt  has  a 
strong  affinity  for  water,  and  also  for  hydrochloric  acid  gas.  A  solution 
of  cupric  sulphate  dissolves  metallic  iron,  the  copper  being  precipitated 
from  the  solution  at  the  same  time  in  a  spongy  mass. 


Anhydrous  Cupric  Sulphate.     CuSO4. 

The  property  anhydrous  cupric  sulphate  possesses  of  absorbing 
hydrochloric  acid  gas  makes  it  useful  in  the  determination  of  carbon 
by  combustion,  and  it  is  best  prepared  for  this  purpose  as  follows. 
Heat  crystals  of  cupric  sulphate,  about  the  size  of  a  coffee  bean,  in  a 
porcelain  dish  until  the  blue  color  of  the  crystals  disappears  and  they 
become  white.  Transfer  while  still  hot  to  a  dry,  glass-stoppered  bottle. 


54  REAGENTS. 

Anhydrous  Cuprous  Chloride.     CuCl. 

To  prepare  the  granulated  salt  for  use  as  an  absorbent  of  hydrochloric 
acid  and  chlorine  in  carbon  determinations,  moisten  the  ordinary  powdered 
salt  of  commerce  in  a  porcelain  dish  and  rub  it  up  with  a  glass  rod  into 
little  lumps  about  the  size  of  a  coffee  bean.  Heat  it  gradually  until 
the  water  is  expelled  and  the  lumps,  which  will  be  dark  brown  in  color, 
harden.  Transfer  to  a  glass-stoppered  bottle. 

Cupric  Chloride.      CuCl2  +  Aq. 

To  prepare  cupric  chloride  for  use  in  dissolving  iron  or  steel  for 
the  determination  of  carbon,  grind  up  equal  weights  of  cupric  sulphate 
and  common  salt  in  a  porcelain  mortar,  and  pour  over  the  mixture  a 
small  amount  of  water  heated  to  from  50°  to  60°  C.  The  liquid  becomes 
emerald-green  in  color,  and  deposits  upon  evaporation  sodium  sulphate. 
Decant  from  the  deposited  salt  and  evaporate  again  until  the  solution 
is  reduced  to  a  very  small  bulk.  Cool,  and  decant  from  the  remainder 
of  the  sodium  sulphate  and  the  excess  of  sodium  chloride.  By  further 
evaporation  and  cooling  the  cupric  chloride  may  be  obtained  in  the  form 
of  green  crystals.  These  crystals  are  deliquescent.  The  solution  should 
be  diluted  and  filtered  through  asbestos. 

Ammonium-Copper   Chloride.     2(NH4Cl),CuCl2,2H2O. 
Potassium-Copper  Chloride.     2(KCl),CuCl2,2H2O. 

Ammonium-copper  chloride  is  a  bluish-green  crystalline  salt,  quite 
soluble  in  water. 

Potassium-copper  chloride  is  bluish-green  likewise  and  more  soluble 
than  the  ammonium  salt.  The  recent  experiments  of  the  American 
members  of  the  International  Steel  Standards  Committee  have  shown 
that  ammonium-copper  chloride  is  nearly  always  impure,  from  the 
presence  of  hydrocarbons  in  the  ammonium  chloride,  derived  probably 
from  the  gas  liquor  from  which  ammonia  salts  are  distilled.  These 
hydrocarbons  unite  with  the  carbonaceous  residue  liberated  from  steel 


METALS  AND    METALLIC  SALTS.  55 

and  iron  in  the  process  of  determining  carbon,  and  of  course  vitiate 
the  results.  Several  recrystallizations  free  the  salt  to  a  certain  extent 
from  this  impurity.  The  use  of  the  potassium  salt  is  not  open  to 
this  objection. 

To  prepare  these  salts  proceed  as  follows.  Dissolve  107  parts  of 
ammonium  chloride  or  149.1  parts  of  potassium  chloride  and  170.3 
parts  of  crystallized  cupric  chloride  (CuCl2,2H2O)  in  water  and  crystallize 
out  the  double  salt.  Dissolve  about  300  grammes  of  the  double  salt 
in  I  litre  of  water,  filter  through  ignited  asbestos,  and  preserve  for 
use  in  glass-stoppered  bottles. 

Cupric  Oxide.     CuO. 

Cupric  oxide,  both  fine  and  coarse,  for  combustions  is  easily  obtained. 
It  may  be  prepared  as  follows.  Dissolve  metallic  copper  in  nitric  acid, 
evaporate  to  dryness  in  a  porcelain  dish,  transfer  it  to  a  Hessian  crucible, 
and  heat  it  in  a  furnace  until  no  more  nitrous  fumes  are  given  off. 
Keep  the  crucible  well  covered  to  prevent  any  coal  getting  into  it,  and 
avoid  raising  the  heat  too  high,  or  the  mass  will  fuse.  Stir  it  from  time 
to  time,  and  when  finished  the  oxide  pn  top  will  be  in  a  fine  powder, 
while  that  in  the  bottom  of  the  crucible  will  have  sintered.  Rub  it  up 
in  a  mortar  and  pass  through  a  fine  metal  sieve.  Keep  the  two  kinds, 
fine  and  coarse,  in  separate  glass-stoppered  bottles,  carefully  covered 
to  protect  them  from  dust. 

Iron  Wire. 

Very  fine  soft  piano-forte  wire  is  the  best  form  of  iron  to  use  when 
standardizing  solutions  of  potassium  permanganate  or  bichromate  by 
metallic  iron.  Wrap  one  end  of  a  piece  of  wire,  about  2  feet  (610  mm.) 
long  around  a  lead-pencil,  and,  using  this  as  a  handle,  draw  the  wire 
several  times  through  a  piece  of  fine  emery-cloth,  then  through  a  fold 
of  dry  filter-paper,  then,  holding  the  wire  with  the  paper,  wrap  it  around 
the  pencil.  Cut  off  the  end  that  has  not  been  cleaned,  and  the  little 
spiral  of  wire  will  be  in  a  convenient  form  for  weighing. 


56  REAGENTS. 

Ferrous  Sulphate.     PeSO4,7H2O. 

Ferrous  sulphate  (green  vitriol,  or  copperas)  is  a  bluish-green  crystal- 
line salt,  soluble  in  1.64  parts  of  water  at  10°  C.,  and  in  0.3  part  at  100° 
C.  It  is  insoluble  in  alcohol.  The  crystals  lose  6  molecules  of  water 
when  heated  to  114°  C.,  but  retain  the  last  molecule  even  at  280°  C. 
Heated  to  a  red  heat  the  anhydrous  sulphate  is  decomposed,  giving  off 
sulphurous  acid  and  leaving  a  basic  ferric  sulphate,  which  at  a  higher 
temperature  is  entirely  decomposed,  leaving  only  ferric  oxide.  To  prepare 
the  crystals  for  use  in  volumetric  analysis,  add  alcohol  to  the  aqueous 
solution  of  the  ferrous  sulphate,  when  the  salt  is  precipitated  as  a  bluish- 
white  powder.  Filter,  wash  with  alcohol,  dry  thoroughly,  and  preserve 
in  glass-stoppered  bottles.  The  salt  prepared  in  this  way  remains  unaltered 
for  a  long  time. 


Ferrous-Ammonium  Sulphate.     FeSO4(NH4)2SO4,6H2O. 

Ferrous-ammonium  sulphate  is  a  light  green  crystalline  salt,  soluble  in 
2.8  parts  of  water  at  16.5°  C.  It  may  be  prepared  as  follows.  Dissolve  276 
grammes  of  crystallized  ferrous  sulphate  in  water,  filter,  and  add  to  the 
filtrate  a  clear  solution  of  ammonium  sulphate  ( (NH4)2SO4,  Glauber's  Sal 
Secretum),  evaporate  down,  and  allow  the  double  salt  to  crystallize  out. 
Drain  the  crystals,  wash  slightly  with  cold  water,  and  dry  on  blotting- 
paper.  When  perfectly  dry,  preserve  in  a  glass-stoppered  bottle.  The 
crystals  remain  unaltered  for  a  long  time  even  in  moist  air.  They  contain 
exactly  \  their  weight  of  metallic  iron. 


Mercurous  Nitrate.     HgNO3,H2O. 

To  prepare  this  salt,  pour  cold,  moderately  strong  nitric  acid  on  an 
excess  of  metallic  mercury,  and  when  the  violent  action  has  subsided 
pour  ofT  the  acid  and  allow  the  salt  to  crystallize  out  by  the  cooling  of 
the  acid.  The  salt  is  soluble  in  a  small  amount  of  water,  but  a  large 
amount  decomposes  it  into  a  basic  salt  and  free  acid. 


METALS  AND   METALLIC  SALTS.  57 

Mercuric  Oxide.     HgO. 

Mercuric  oxide  is  a  light  orange-yellow  substance  when  prepared  by 
precipitation  from  a  mercuric  salt.  To  a  dilute  solution  of  mercuric 
chloride  add  a  slight  excess  of  caustic  potash,  allow  the  precipitate  to  settle, 
wash  it  thoroughly  by  decantation  with  hot  water,,  and  finally  wash  it  into 
a  glass-stoppered  bottle.  It  is  used  shaken  up  with  water. 

Lead  Chromate.     PbCrO4. 

Fused  lead  chromate  is  a  dark  brown  mass  showing  a  radiated 
structure,  and  when  powdered  it  is  dark  yellow  in  color,  very  heavy,  and 
slightly  hygroscopic.  It  is  easily  obtained  very  pure,  but  may  be  made 
as  follows.  Dissolve  lead  acetate  in  water,  add  a  little  acetic  acid,  filter, 
and  precipitate  by  a  solution  of  potassium  bichromate.  Wash  by  decanta- 
tion, and  finally  on  linen,  dry,  and  heat  in  a  Hessian  crucible  until  the 
mass  is  just  fused.  Pour  on  a  polished  iron  slab,  grind  in  a  clean  mortar, 
and  preserve  the  powder  in  glass-stoppered  bottles,  covered  to  exclude 
dust.  Lead  chromate  heated  to  a  full  red  heat  gives  off  oxgyen  and  is 
reduced  to  a  mixture  of  basic  lead  chromate  and  chromium  oxide. 

Lead  Peroxide.     PbO2. 

Lead  peroxide  is  rather  difficult  to  obtain  in  a  state  of  purity  ;  it  is 
liable  to  contain  lead  nitrate  and  manganese  oxide.  The  latter  element 
interferes  materially  with  its  use  as  a  reagent  in  the  determination  of 
manganese  by  the  color  test.  It  should  always  be  carefully  examined  by 
boiling  with  dilute  nitric  acid,  and,  if  it  imparts  any  color  to  the  solution, 
must  be  promptly  rejected.  It  may  readily  be  prepared  by  digesting  red 
oxide  of  lead  in  dilute  nitric  acid,  decanting  off  the  lead  nitrate,  and  washing 
the  residue  thoroughly  with  hot  water.  By  this  treatment  the  red  oxide 
is  decomposed  into  lead  protoxide,  which  dissolves  in  the  nitric  acid,  and 
lead  peroxide,  which  remains  insoluble.  Lead  peroxide  is  a  heavy  brown 
powder,  which,  when  heated,  gives  off  oxygen  and  is  converted  into  red 
lead  or  lead  protoxide. 


58  REAGENTS. 

Lead  Oxide  dissolved  in  Caustic  Potash. 

Pour  a  cold  solution  of  lead  nitrate  into  caustic  potash,  1.27  sp.  gr., 
stirring  constantly  to  dissolve  the  lead  oxide,  which  precipitates.  Add  the 
lead  nitrate  until  a  permanent  precipitate  is  produced.  Allow  this  to  settle, 
and  siphon  the  clear  liquid  into  a  glass-stoppered  bottle.  It  is  well  to  coat 
the  stopper  with  a  little  paraffine,  to  prevent  its  sticking. 

Platinic  Chloride  Solution. 

Dissolve  platinum-foil  in  hydrochloric  acid,  adding  nitric  acid  from 
time  to  time,  evaporate  to  dryness  on  the  water-bath,  redissolve  in  hydro- 
chloric acid,  and  evaporate  again  to  drive  off  the  nitric  acid.  Redissolve 
in  water  with  the  addition  of  a  few  drops  of  hydrochloric  acid,  filter,  and 
preserve  in  a  bottle  the  stopper  and  neck  of  which  are  protected  by  a 
ground-glass  cap  to  prevent  access  of  ammonia  to  the  solution. 

Metallic  Zinc. 

Melt  zinc,  which  should  be  as  free  as  possible  from  lead  and  iron,  in 
a  Hessian  crucible,  and  pour  it  in  a  thin  stream  from  a  height  of  four  or 
five  feet  into  a  bucket  of  cold  water,  giving  the  crucible  a  circular  motion 
to  prevent  the  zinc  from  falling  in  exactly  the  same  place  all  the  time. 
Pour  off  the  water,  dry  the  granulated  zinc,  and  preserve  it  in  bottles 
for  use. 

Zinc  Oxide  in  Water. 

Emmerton  *  suggests  the  following  method  of  preparing  this  reagent. 
Dissolve  ordinary  zinc  white  in  hydrochloric  acid,  add  the  zinc  white  until 
there  is  an  excess  which  will  not  dissolve,  then  add  a  little  bromine-water, 
heat  the  solution,  filter,  and  precipitate  the  zinc  oxide  by  ammonia,  being 
careful  to  avoid  an  excess.  Wash  thoroughly  by  decantation,  and  then 
wash  into  a  bottle.  Shake  the  bottle  well,  to  diffuse  the  oxide  through 
the  water,  before  using. 

*  Trans.  Am.  Inst.  Min.  Engineers,  x.  201. 


REAGENTS  FOR   DETERMINING   PHOSPHORUS.  59 

REAGENTS  FOR  DETERMINING  PHOSPHORUS. 

Magnesia  Mixture. 

Dissolve  110  grammes  of  crystallized  magnesium  chloride  (MgCl2  -j- 
6H2O)  or  50  grammes  of  the  anhydrous  salt  in  water,  and  filter.  Dissolve 
28  grammes  of  ammonium  chloride  in  water,  add  a  little  bromine-water 
and  a  slight  excess  of  ammonia,  and  filter.  Add  this  solution  to  the 
solution  of  magnesium  chloride,  add  enough  ammonia  to  make  the 
solution  smell  decidedly  of  ammonia,  dilute  to  about  2  litres,  transfer 
to  a  bottle,  shake  vigorously  from  time  to  time,  allow  it  to  stand  for 
several  days,  and  filter  into  a  small  bottle  as  required  for  use.  10  c.c. 
of  this  solution  will  precipitate  about  0.15  gramme  phosphoric  acid. 

Molybdate  Solution. 

Weigh  100  grammes  of  pure  molybdic  anhydride,  mix  it  thoroughly 
in  a  beaker  with  400  c.c.  of  cold  distilled  water  and  add  80  c.c.  of  strong 
ammonia  (0.90  sp.  gr.).  When  solution  is  complete,  filter  and  pour  the 
filtered  solution  slowly  with  constant  stirring  into  a  mixture  of  400  c.c. 
of  strong  nitric  acid  (1.42  sp.  gr.)  and  600  c.c.  of  distilled  water.  Allow 
to  settle  for  24  hours  and  filter.  A  solution  prepared  in  this  way  will 
keep  for  several  months  even  in  hot  weather  without  any  deposition 
of  molybdic  acid. 


METHODS   FOR  THE  ANALYSIS 

OF 

PIG-IRON,  BAR-IRON,  AND  STEEL 


DETERMINATION    OF    SULPHUR. 

By  Evolution  as  Hydrogen  Sulphide. 

KARSTEN  was  the  first  to  suggest  dissolving  iron  or  steel  in  hydro- 
chloric acid,  or  dilute  sulphuric  acid,  and  collecting  the  evolved 
hydrogen  sulphide  by  absorbing  it  in  a  solution  of  a  metallic  salt. 
He  recommended  cupric  chloride. 

Absorption  by  Alkaline  Solution  of  Lead  Nitrate. 

The  apparatus,  Fig.  47,  shows  the  usual  arrangement  for  carrying 
out  the  process,  with  the  addition  of  the  generating-bottles  for  supply- 
ing hydrogen  gas.  This  is  the  apparatus  described  under  the  head  of 
."Apparatus  for  Generating  Carbonic  Acid  Gas,"  page  42.  The  wash- 
bottle  A  contains  an  alkaline  solution  of  lead  nitrate,  and  is  connected 
with  the  funnel-tube  by  the  rubber  tube  B,  and  a  small  piece  of  glass 
tubing,  C,  turned  at  a  right  angle  with  one  end  drawn  down  and  covered 
with  a  short  piece  of  rubber  tubing.  This  fits  in  the  neck  of  the  bulb 
of  the  funnel-tube  and  makes  a  tight  joint.  The  analytical  process  is 
conducted  as  follows  : 

Place    10  grammes  *  of  borings  or  drillings,  free  from  lumps,  in  the 

*  A  5-factor  weight  (6.878  grammes)  is  a  better  amount  to  take,  as,  when  the  weight  of  barium 
sulphate  found  is  multiplied  by  two,  each  milligramme  is  one- thousandth  of  a  per  cent,  of  sulphur. 
60 


DETERMINATION   OF  SULPHUR. 


6l 


previously  dried  flask  D,  and  close  it  with  the  rubber  stopper  fitted  with 
a    funnel-tube   and   a   delivery-tube.     The   outlet-tube    from    the    flask    D 


connects    with    the    tube    F,    reaching    almost    to    the    bottom    of    the 
Erlenmeyer    flask    H.      Pour    into    each    of  the    flasks    H    about    20    or 


62  ANAL  YSIS   OF  IRON  AND   STEEL. 

30  c.c.  of  potassium  hydrate  solution  of  lead  nitrate  *  and  enough  water 
to  fill  them  two-thirds  full.  Connect  the  apparatus,  and  run  a  slow 
stream  of  hydrogen  through  until  all  the  air  is  expelled,  then  close 
the  glass  stopcock  of  the  funnel-tube,  and  shut  off  the  supply  of 
hydrogen  by  closing  the  small  glass  stopcock  K.  If  the  connections 
are  all  tight,  the  liquid  will  not  recede  in  the  tube  F.  When  this  is 
assured,  disconnect  the  tube  C,  and  fill  the  bulb — which  should  be  of 
about  100  c.c.  capacity — with  a  mixture  of  50  c.c.  of  strong  hydrochloric 
acid  and  50  c.c.  of  water.  Replace  the  tube  C,  turn  on  the  hydrogen, 
and  open  the  stopcock  of  the  funnel-tube,  so  as  to  allow  the  acid  to  flow 
into  the  flask  D.  When  the  acid  has  all  run  into  the  flask,  regulate  the 
flow  of  the  hydrogen  so  that  the  gas  shall  pass  through  the  solutions 
in  the  flasks  H,  H'  as  rapidly  as  possible,  and  heat  the  flask  D.  When 
the  solution  in  the  flask  D  has  boiled  for  fifteen  minutes,  and  all  the 
metal  has  dissolved,  remove  the  source  of  heat  and  continue  the  current 
of  hydrogen  for  about  ten  minutes,  regulating  its  flow  by  means  of 
the  stopcock  K,  to  prevent  any  reflux  of  the  liquid  in  H,  which  might 
be  caused  by  the  cooling  of  the  flask  D.  Shut  off  the  hydrogen, 
disconnect  the  apparatus,  and  wash  the  contents  of  the  flask  H  into 
a  No.  2  Griffin's  beaker.  Unless  a  precipitate  of  lead  sulphide  appears 
in  the  second  flask  H',  it  need  not  be  emptied,  but  the  same  solution 
can  be  used  over  again  for  the  next  analysis.  Collect  the  precipitate 
on  a  small  filter,  wash  it  once  or  twice  with  hot  water,  and,  while 
still  moist,  throw  the  filter  and  precipitate  back  into  the  beaker,  in 
which  have  been  placed  the  instant  before  some  powdered  potassium 
chlorate  and  from  5  to  20  c.c.  of  strong  hydrochloric  acid,  according 
to  the  amount  of  the  precipitate  of  lead  sulphide.  Allow  it  to  stand 
in  a  warm  place  until  the  fumes  shall  have  partly  passed  ofT,  then 
add  about  twice  its  volume  of  hot  water,  and  filter  into  a  No.  I 
beaker.  Wash  with  hot  water,  heat  the  filtrate  to  boiling,  and  add 
ammonia  until  the  solution  is  slightly  alkaline  to  litmus-paper.  Acidu- 
late with  a  few  drops  of  hydrochloric  acid,  add  from  5  to  10  c.c.  of  barium 

*  See  page  58. 


DETERMINATION   OF  SULPHUR.  63 

chloride  solution,*  boil  15  or  20  minutes,  and  stand  aside  for  half  an 
hour.  Filter  the  precipitate  of  barium  sulphate,  preferably  on  a  Gooch 
perforated  crucible,  wash  with  hot  water,  ignite,  and  weigh  as  barium 
sulphate,  which  contains  13.75  per  cent,  sulphur.  It  is  always  well  to 
test  the  alkaline  filtrate  from  the  lead  sulphide  with  a  few  drops  of 
the  lead  solution,  for  it  might  happen  that  all  the  lead  would  be  pre- 
cipitated from  the  solution  as  sulphide,  and  an  excess  of  hydrogen 
sulphide  remain  in  the  solution  as  potassium  sulphide. 

The  entire  operation  described  above  can  be  performed  in  about  two 
and  a  half  hours,  and  is,  in  my  opinion,  the  most  accurate  method  known 
for  the  determination  of  sulphur  in  steel. 

Absorption  by  Ammoniac al  Solution  of  Cadmium  Sulphate. 

T.  T.  Morrell  f  passes  the  evolved  gas  into  an  ammoniacal  solution  of 
cadmium  sulphate.  Prepare  a  solution  of  cadmium  sulphate  of  convenient 
strength,  and  add  enough  ammonia  to  redissolve  the  precipitate  and  give 
a  clear  solution.  Place  the  solution  in  the  bottles  H,  H',  and  proceed  as 
usual.  Filter  the  precipitate  of  cadmium  sulphide  in  a  counterpoised 
filter,  wash  with  water  containing  a  little  ammonia,  dry  at  100°  C.,  and 
weigh  as  cadmium  sulphide,  which  contains  22.25  Per  cent,  of  sulphur. 
Instead  of  cadmium  sulphate,  cadmium  chloride  seems  to  be  now  more 
generally  in  use. 

Absorption  by  Ammoniacal  Solution  of  Silver  Nitrate. 

Berzelius  proposed  the  use  of  a  dilute  solution  of  silver  nitrate  made 
alkaline  by  ammonia.  The  method  of  procedure  is  as  follows.  Dissolve 
I  gramme  of  silver  nitrate  in  a  small  quantity  of  water,  and  make  it 
strongly  alkaline  with  ammonia ;  pour  about  two-thirds  of  the  solution 
into  the  first  of  the  bottles  H,  and  the  remainder  into  the  second,  and 
fill  up  to  the  proper  level  with  water.  Proceed  exactly  as  described  above 
until  the  silver  sulphide  has  been  filtered  off  and  washed.  Dry  this 

*  See  page  51.  f  Chem.  News,  xxviii.  229. 


64 


ANAL  YSIS    OF  IRON  AND   STEEL. 


precipitate  carefully  at  a  low  temperature  —  say  100°  C.  —  and  brush  it  care- 
fully into  a  small,  dry  beaker,  returning  the  filter  to  the  funnel.  Pour  into 
the  bottles  H,  should  any  of  the  sulphide  remain  adhering  to  the  sides, 
2O  or  30  c.c.  strong  nitric  acid,  and  when  it  is  all  dissolved,  pour  the  acid 
in  the  filter,  allowing  it  to  run  into  the  beaker  containing  the  silver  sulphide, 
and  wash  out  the  bottles  with  a  little  nitric  acid,  allowing  this  to  run  over 
the  filter  also.  Digest  the  silver  sulphide  until  it  is  all  dissolved,  then 
dilute  with  hot  water,  add  an  excess  of  hydrochloric  acid,  and  filter  off 
the  silver  chloride.  Add  a  small  amount  of  sodium  carbonate,  and 
evaporate  nearly  dry,  dilute,  add  a  few  drops  of  hydrochloric  acid,  filter 
if  necessary,  and  precipitate  as  before  by  barium  chloride.  Even  when 
the  sample  contains  no  sulphur  a  slight  precipitate  of  silver  carbide  may 
be  thrown  down  by  the  carburetted  hydrogen  evolved  from  the  iron  or 
steel  by  the  action  of  the  acid. 

Absorption  and  Oxidation  by  Bromine  and  Hydrochloric  Acid. 

Fresenius  *  suggested  passing  the  evolved  gases  through  a  solution  of 
bromine  in  hydrochloric  acid,  which  has  the  advantage  of  oxidizing  the 

hydrogen  sulphide  at  once,  but  the  disadvantage 
of  filling  the  room  with  bromine-fumes  unless  the 
apparatus  is  placed  under  a  hood  with  a  good 
draft.  It  is  necessary  when  using  this  method 
to  avoid  bringing  the  bromine-fumes  in  contact 
with  rubber  stoppers.  Instead  of  the  bottles  H, 
attach  to  the  exit-tube  a  bulb-tube  of  the  shape 
shown  in  Fig.  48,  containing  from  3  to  5  c.c.  of 
bromine  and  enough  hydrochloric  acid  to  fill  the 
bulb-tube  to  the  marks  shown  in  the  cut.  When 
the  operation  is  finished,  wash  the  contents  of 
the  bulb-tube  out  into  a  beaker,  heat  until  the  bromine  is  all  driven  off, 
neutralize  by  ammonia,  and  precipitate  the  sulphuric  acid  exactly  as  de- 
scribed on  page  62.  Instead  of  neutralizing  by  ammonia,  the  hydrochloric 


FIG. 


Fresenius,  Zeitschrift,  xiii.  37. 


DETERMINATIOAr  OF  SULPHUR.  65 

acid  solution  may  be  evaporated  down  nearly  to  dryness  after  adding  a 
little  sodium  carbonate  or  the  solution  of  barium  chloride  ;  but  repeated 
experiments  have  shown  that  barium  sulphate  is  practically  insoluble  in 
ammonium  chloride,  so  that  the  plan  of  neutralizing  by  ammonia,  being 
the  shorter  and  less  troublesome,  is  to  be  preferred. 

Absorption  and  Oxidation  by  Potassium  Permanganate. 

Drown  *  suggested  the  use  of  potassium  permanganate  solution  as 
an  absorbent  and  oxidizer,  the  process  being  carried  on  as  follows.  Make 
a  solution  of  potassium  permanganate,  5  grammes  to  the  litre  of  water, 
and  fill  the  bottles  H  to  the  proper  height  with  this  liquid,  using  three 
bottles,  however,  instead  of  two,  and  proceed  with  the  operation  as  before 
described,  being  careful  to  avoid  a  rapid  evolution  of  the  gas.  Wash  the 
contents  of  the  bottles  H  into  a  clean  beaker,  dissolve  any  manganese 
oxide  that  may  adhere  to  the  sides  of  the  bottles  in  hydrochloric"  acid, 
add  this  to  the  solution  in  the  beaker,  and  then  add  enough  hydrochloric 
acid  to  entirely  decompose  the  permanganate.  Boil  until  the  solution  is 
colorless,  filter  if  necessary,  and  precipitate  by  barium  chloride.  Allow 
it  to  stand  overnight,  filter,  wash,  ignite,  and  weigh  the  barium  sulphate. 

Absorption  and  Oxidation  by  Hydrogen  Peroxide. 

Craig  f  suggested  the  use  of  ammoniacal  solution  of  hydrogen  per- 
oxide in  the  absorbing-bottles.  Attach  to  the  exit-tube  of  the  flask  D 
(Fig.  47)  a  nitrogen-bulb  of  the  usual  form  (Fig.  48),  in  which  have  been 
placed  4  c.c.  of  hydrogen  peroxide  and  16  c.c.  of  ammonia,  and  proceed 
as  before  directed.  When  the  operation  is  finished,  wash  the  contents  of 
the  nitrogen  bulb  into  a  small  beaker,  acidulate  slightly  with  hydrochloric 
acid,  boil,  add  barium  chloride,  and  determine  the  amount  of  barium 
sulphate  as  usual.  As  hydrogen  peroxide  always  contains  sulphuric  acid, 
the  amount  must  be  carefully  determined  in  each  fresh  lot  of  the  hydrogen 
peroxide,  and  the  proper  correction  made  for  the  volume  used. 

*  Journal  Inst.  Min.  Engineers,  ii.  224.  f  Chem.  News,  xlvi.  199. 


66  ANAL  YSIS   OF  IRON  AND   STEEL. 

By  Oxidation  and  Solution. 

Many  chemists  still  prefer  the  method  of  oxidizing  and  dissolving  the 
metal  and  precipitating  the  sulphuric  acid  in  the  solution  by  barium 
chloride.  The  details  are  as  follows.  Treat  5  grammes  of  drillings  in  a 
No.  4  Griffin's  beaker,  covered  by  a  watch-glass,  with  40  c.c.  of  strong 
nitric  acid.  This  requires  care,  for  drillings  of  bar-iron  and  low  steel  are 
often  acted  on  so  violently,  even  by  strong  nitric  acid,  as  to  cause  the 
solution  to  boil  over.  In  this  case  it  is  best  to  place  the  beaker  in  a  dish 
containing  a  little  cold  water  and  to  add  the  acid  gradually.  When  all  the 
acid  has  been  added  and  the  action  has  ceased,  some  small  particles 
generally  remain  undissolved,  and  their  solution  is  effected  by  heating  the 
beaker  on  the  sand-bath  and  finally  by  adding  a  few  drops  of  hydrochloric 
acid.  With  pig-iron  and  steel  there  is  usually  no  action  in  the  cold,  and 
in  this  case  heat  the  beaker  carefully  until  the  action  begins,  then  stand 
the  beaker  in  a  cooler  place,  and  if  the  action  becomes  very  violent,  stand 
the  beaker  in  cold  water  until  it  moderates.  Very  high  carbon  steels 
dissolve  with  great  difficulty  even  in  boiling  acid ;  but  the  solution  may 
be  hastened  by  adding  a  few  drops  of  hydrochloric  acid  from  time  to  time. 
When  solution  is  complete  and  only  particles  of  graphite  and  silica  remain 
undissolved,  which  is  shown  by  the  residue  being  entirely  flotant,  remove 
the  cover,  add  a  little  sodium  carbonate,  and  evaporate  the  solution  to 
dryness  in  the  air-bath.  The  addition  of  the  sodium  carbonate  is  to 
prevent  any  possible  loss  of  sulphuric  acid,  which  might  otherwise  occur 
by  the  decomposition  of  the  ferric  sulphate  at  a  high  temperature.  Re- 
move the  beaker  from  the  air-bath,  and  when  cold  add  30  c.c.  hydrochloric 
acid,  and  heat  until  the  ferric  oxide  is  dissolved,  evaporate  again  to  dryness 
to  render  the  silica  insoluble,  redissolve  in  hydrochloric  acid,  evaporate 
until  the  ferric  chloride  begins  to  separate  out,  add  2  c.c.  hydrochloric 
acid  and  a  little  water.  Filter  and  wash,  being  careful  that  the  total 
filtrate  and  washings  shall  not  exceed  100  c.c.  in  volume.  Heat  the  filtrate 
to  boiling,  add  10  c.c.  saturated  solution  of  barium  chloride,  and  allow  it 
to  stand  in  the  cold  overnight.  Filter,  wash  with  a  little  very  dilute  hydro- 
chloric acid,  and  finally  with  cold  water ;  dry,  ignite,  and  weigh  as  barium 


DETERMINATION  OF  SULPHUR.  67 

sulphate.  If  this  ignited  precipitate  is  reddish  in  color,  it  shows  that 
ferric  oxide  has  been  precipitated  with  the  barium  sulphate.  In  this  case 
fuse  with  sodium  carbonate,  dissolve  in  water,  filter,  acidulate  the  filtrate, 
and  precipitate  as  before.  Or,  filter  the  aqueous  solution  of  the  fusion, 
dissolve  in  hydrochloric  acid,  precipitate  by  ammonia,  weigh  the  ferric 
oxide,  and  subtract  from  the  weight  of  barium  sulphate. 

Bamber's  Method  (for  Pig-Iron). 

The  investigations  of  Phillips  *  and  Matthewman  f  have  shown  conclu- 
sively that  in  many  pig-irons  the  evolution  method  fails  to  give  the  full 
sulphur  contents.  This  seems  to  be  due  to  the  formation  of  organic 
sulphides,  probably  of  the  mercaptan  series,  and  not  to  the  presence  of 
copper  or  arsenic,  as  has  been  supposed.  As  those  compounds  are  quite 
volatile  and  very  difficult  to  oxidize,  some  portions  seem  to  pass  through 
the  absorbing  solutions,  while  under  certain  circumstances  other  portions 
remain  in  the  evolution  flask  with  great  persistency  and  are  expelled  only 
after  long  boiling. 

The  only  practicable  method  for  pig-irons  of  this  character,  therefore, 
is  the  following.  Dissolve  5  grammes  or  a  5-factor  weight  (6.878 
grammes)  in  strong  nitric  acid,  add  10  grammes  of  sodium  carbonate, 
wash  into  a  platinum  or  porcelain  dish,  evaporate  to  dry  ness  and  ignite 
over  an  alcohol  flame.  Treat  with  water  with  the  addition  of  a  little 
sodium  carbonate,  filter,  and  wash  with  water  containing  sodium  carbonate. 
Acidulate  with  hydrochloric  acid,  evaporate  to  dryness,  redissolve  in  water 
with  a  few  drops  of  hydrochloric  acid,  and  precipitate  boiling  with  barium 
chloride. 

Notes  and  Precautions. 

There  are  three  precautions  to  be  observed  in  using  the  oxidation 
method. 

i.  The  sample  should  be  dissolved  in  strong  nitric  acid,  as,  when  dilute 
nitric  acid,  or  even  aqua  regia,  is  used,  some  sulphur  seems  to  escape 
oxidation. 

*  Journal  American  Chem.  Society,  xvii.  89 1 . 

|  Journal  West  of  Scotland  Iron  and  Steel  Institute,  iii.  27. 


68  ANAL  YSIS   OF  IRON  AND   STEEL. 

2.  The  amount  of  acid  in  the  solution  from  which  the  barium  sulphate 
is  precipitated  must  be  most  carefully  regulated,  as  well  as  the  absolute 
volume  of  the  solution. 

3.  The   reagents  used  must  be  examined  for  sulphuric  acid.     This  is 
best  done  as  follows.     Measure  into  a  beaker  the  total  amount  of  acid, 
both  nitric  and  hydrochloric,  used  in  the  determination,  add  a  little  sodium 
carbonate  and  evaporate  to  dryness.     Redissolve  in   1 5   c.c.  of  water  and 
5  or   10  drops  of  hydrochloric  acid,  filter,  heat  to  boiling,  add   10  c.c.  of 
barium  chloride,  boil  10  or   15   minutes,  allow  to  settle,  filter,  wash,  ignite, 
and  weigh  as  barium  sulphate.      The  amount  found  is  to  be  subtracted 
from  the  total  weight  of  barium  sulphate  found  in  the  sample. 

In  the  use  of  the  evolution  method  for  steels,  the  results  obtained 
vary  somewhat  with  the  solution  used  for  absorbing  the  hydrogen 
sulphide,  and  I  am  satisfied  that  the  best  absorbent  is  the  alkaline 
solution  of  lead  nitrate.  I  have  never  failed,  so  far  as  I  know,  in 
getting  correct  results  with  this  absorbent  in  any  steel.  The  evolution 
of  the  gas  should  be  as  rapid  as  possible,  as  there  seems  to  be  no 
danger  of  any  hydrogen  sulphide  passing  the  liquid  in  the  first  flask, 
and  the  operation  is  naturally  shortened.  If  the  solution  containing 
the  precipitated  barium  sulphate  is  boiled  vigorously  for  15  or  20 
minutes,  it  is  not  necessary  to  allow  it  to  stand  more  than  half  an 
hour,  so  that  a  determination  can  be  made  in  two  hours,  or  two  hours 
and  a  half,  without  any  trouble. 

RAPID    METHOD. 

Volumetric  Determination  by  Iodine. 

This  method,  suggested  by  Elliott,*  involves  the  evolution  of  the 
sulphur  as  hydrogen  sulphide,  its  absorption  in  a  solution  of  sodium 
hydroxide,  and  titration  by  iodine  in  potassium  iodide.  It  requires  a 
standard  solution  of  iodine,  a  standard  solution  of  sodium  thiosulphate,  a 
starch  solution,  and  a  standard  solution  of  potassium  bichromate. 

*  Chem.  News,  xxiii.  61. 


RAPID   METHOD   FOR   SULPHUR.  69 

Iodine  Solution. 

Dissolve  6.5  grammes  pure  iodine  in  water  with  9  grammes  potassium 
iodide,  and  dilute  to  I  litre. 

Sodium  Thiosulphate  Solution. 

Dissolve  25  grammes  sodium  thiosulphate  in  water,  and  dilute  to 
I  litre. 

Starch  Solution. 

Weigh  into  a  porcelain  or  Wedgwood  mortar  I  gramme  of  pure 
wheat  starch,  and  rub  it  to  a  thin  cream  with  water.  Pour  it  into 
150  c.c.  boiling  water,  allow  it  to  stand  until  cold,  and  decant  the 
clear  solution.  The  addition  of  10  or  15  c.c.  glycerine  makes  the 
solution  keep  better.  It  is  better,  however,  to  make  a  fresh  starch 
solution  every  few  days. 

Dr.  Waller  recommends  Miiller's  suggestion  of  grinding  the  starch 
with  a  strong  solution  of  potassium  or  sodium  hydroxide  and  dissolving 
in  hot  water  for  use.  It  keeps  indefinitely. 

Potassium  Bichromate  Solution. 

Dissolve  5  grammes  pure  potassium  bichromate  in  water,  and  dilute 
to  I  litre. 

All  these  solutions  should  be  placed  in  glass-stoppered  bottles  and 
kept  in  a  dark  place. 

Standardizing-  the  Solutions. 

Standardize  the  bichromate  solution  as  directed  in  the  "  Analysis  of 
Iron  Ores."  When  potassium  bichromate  is  added  to  potassium  iodide 
in  presence  of  free  hydrochloric  acid,  iodine  is  liberated,  in  accordance 
with  the  formula  K2Cr2O7  +  6KI  +  I4HC1  -  8KC1  +Cr2G6  +  ?H2O  +  61, 
or  i  equivalent  of  potassium  bichromate  =  294.5  liberates  6  equivalents 
of  iodine  =  761.1.  Therefore,  by  adding  to  a  solution  of  potassium 
iodide  in  the  presence  of  hydrochloric  acid  a  known  amount  of 
bichromate,  we  can  calculate  the  absolute  amount  of  iodine  liberated, 
and  by  titrating  this  solution  by  the  thiosulphate  solution  we  can 


70  ANAL  YSIS   OF  IRON  AND   STEEL. 

accurately  standardize  the  latter.  The  reaction  which  takes  place  when 
a  solution  of  sodium  thiosulphate  is  acted  on'  by  iodine  is  2NaaS2O3  + 
2\  =  2NaI  -|-  Na2S4O6,  or  2  equivalents  of  thiosulphate  unite  with  2 
equivalents  of  iodine  to  form  sodium  iodide  and  sodium  tetrathionate. 
By  adding  a  few  drops  of  starch  solution  to  a  solution  containing 
iodine,  blue  iodide  of  starch  is  formed,  and  colors  the  solution  as 
long  as  it  contains  free  iodine.  When  enough  thiosulphate  is  added 
to  a  solution  of  this  kind  to  combine  exactly  with  the  iodine,  the  blue 
color  disappears.  Conversely,  upon  adding  a  solution  of  iodine  to  a 
solution  containing  sodium  thiosulphate  and  a  little  starch,  the  sensitive 
blue  color  of  the  iodide  of  starch  will  disappear  as  fast  as  formed 
until  all  the  thiosulphate  has  been  changed  to  tetrathionate,  and  then 
the  first  drop  of  iodine  in  excess  will  change  the  solution  to  a 
permanent  blue.  The  same  thing  holds  true  as  regards  a  solution 
containing  free  hydrogen  sulphide,  the  reaction  being  H2S  -f  2!  = 
2HI  -f  S.  Proceed  therefore  as  follows.  Dissolve  about  i  gramme  of 
pure  potassium  iodide  in  300  c.c.  water,  add  5  c.c.  hydrochloric  acid, 
and  then  25  c.c.  of  the  bichromate  solution,  which  will  liberate  a 
known  amount  of  iodine.  Drop  in  now  the  thiosulphate  solution 
from  a  burette  until  the  iodine  nearly  disappears,  add  a  few  drops 
of  starch  solution,  and  continue  the  thiosulphate  until  the  blue  color 
fades  out  entirely.  The  amount  of  iodine  being  known,  the  value  of 
the  thiosulphate  solution  is  calculated  from  the  reading  of  the  burette. 
Now  allow  to  flow  into  a  beaker  from  a  carefully  graduated  pipette 
25  c.c.  of  the  thiosulphate  solution,  dilute  to  300  c.c.,  add  a  few  drops 
of  the  starch  solution,  and  drop,  from  a  burette,  standard  iodine  solu- 
tion until  the  blue  color  is  permanent.  The  value  of  the  thiosulphate 
solution  being  known,  that  of  the  iodine  solution  is  readily  calculated. 
An  example  will  illustrate  this.  Suppose  we  find  by  titration  that 
I  c.c.  of  our  bichromate  solution  is  equal  to  .00566  gramme  metallic 
iron;  then,  as  the  reaction  is  6FeCl2  +  K2Cr2O7  -f  14UCI  =  3Fe2CI6  + 
2KC1  -\-  Cr2Cl6-(-  7H2O,  I  equivalent  of  potassium  bichromate  =  294.5  is 
equal  to  6  equivalents  of  iron  =  336.  Hence  336  :  294.5  =  .00566  : 
.004961,  or  i  c.c.  of  the  bichromate  solution  contains  .004961  gramme 


RAPID   METHOD   FOR   SULPHUR.  /I 

potassium  bichromate,  and  consequently  25  c.c.  contain  .124025  gramme 
potassium  bichromate.  Then,  as  we  saw  by  the  formula  that  294.5  parts 
bichromate  liberate  761.1  parts  iodine,  we  have  294.5  :  761.1  =  .124025  : 
.32052,  or  25  c.c.  of  the  bichromate  solution  liberate  .32052  gramme  iodine. 
We  now  find  that  it  requires  25.3  c.c.  of  the  thiosulphate  solution  to 
decolorize  the  solution  made  by  adding  25  c.c.  bichromate  solution  to 
the  potassium  iodide;  consequently  each  c.c.  of  the  thiosulphate  contains 
enough  sodium  thiosulphate  to  react  with  .01267  gramme  iodine.  We 
now  measure  out  10  c.c.  of  the  thiosulphate  solution,  dilute  it  to  300 
c.c.,  add  a  few  drops  of  starch  solution,  and  find  that  it  requires  20. 1 
c.c.  of  the  iodide  solution  to  give  the  permanent  blue  color.  Hence 
20.  i  c.c.  =  .1267  gramme  iodine,  or  I  c.c.  iodide  solution  contains 
.006303  gramme  iodine.  As  the  reaction  with  hydrogen  sulphide  is 
H2S  -j-  2!  =  2HI  -f-  S,  it  requires  2  equivalents  of  iodine  to  decompose  I 
equivalent  of  hydrogen  sulphide,  and  the  proportion  is  2!  :  S  :  :  253.7  : 
32.06  :  :  .006303  :  .000796,  or  I  c.c.  iodine  is  equal  to  .000796  gramme 
sulphur. 

The  standard  solutions  once  ready,  the  actual  determination  of  sulphur 
in  a  sample  is  very  simple.  Pour  50  c.c.  of  a  solution  of  caustic  soda, 
i.i  sp.  gr.,  free  from  sulphur,  into  the  first  of  the  bottles  H.  The  second 
need  not  be  used,  but  it  is  a  good  plan  to. keep  a  caustic  potash  solution 
of  lead  nitrate  in  it,  and  attach  it  after  the  other,  to  be  certain  that  no 
hydrogen  sulphide  escapes  the  caustic  soda  solution.  Proceed  with  the 
determination  as  directed  on  page  60,  and  when  finished  wash  the  contents 
of  the  bottle  H  into  a  beaker,  dilute  to  500  c.c.,  acidulate  with  hydro- 
chloric acid,  add  a  few  drops  of  starch  solution,  and  titrate  with  the 
iodide  solution.  See  exactly  how  much  hydrochloric  acid  is  required  to 
acidulate  strongly  50  c.c.  of  the  caustic  soda  solution,  and  this  amount 
can  be  added  at  once,  so  that  no  time  need  be  lost  in  testing  the  solution 
with  litmus  before  titrating. 

Mr.  E.  F.  Wood,*  of  the  Homestead  Steel- Works,  modifies  the  method 
ns  follows.  Pass  the  evolved  gas  into  an  ammoniacal  solution  of  cadmium 

*  Communicated  to  the  author. 


72  ANAL  YSIS   OF  IRON  AND   STEEL. 

sulphate  instead  of  caustic  soda.  Filter,  place  the  filter  containing  the 
precipitate  of  cadmium  sulphide  in  a  beaker  containing  cold  water,  add 
enough  hydrochloric  acid  to  dissolve  the  precipitate,  and  titrate  with  iodide 
solution  as  above  described. 

Mr.  Wood  thinks  that  this  method  has  several  advantages  over  that 
in  which  caustic  soda  is  used  to  absorb  the  hydrogen  sulphide.  The 
hydrocarbon  gases  absorbed  by  the  alkaline  solution  are  gotten  rid  of, 
and  the  error  which  their  presence  may  produce  is  avoided ;  the  bulk  of 
the  precipitate  is  an  indication  of  the  amount  of  sulphur  and  a  guide  to 
the  proper  amount  of  hydrochloric  acid  to  use  for  its  solution,  and  when 
the  cadmium  sulphide  is  filtered  ofT,  only  a  small  amount  of  hydrochloric 
acid  is  required,  and  the  generation  of  heat  from  the  neutralization  of  the 
alkali  is  avoided. 


DETERMINATION    OF    SILICON. 

By  Solution  in  Nitric  and  Hydrochloric  Acids. 
Dissolve  5  grammes  of  drillings  in  40  c.c.  nitric  acid  with  the  pre- 
cautions mentioned  on  page  66 ;  although  when  silicon  alone  is  to  be 
determined,  nitric  acid  of  1.2  sp.  gr.  may  be  used,  when,  in  most  cases, 
the  solution  of  the  drillings  will  be  more  rapid.  Remove  the  cover, 
evaporate  the  solution  to  dryness  in  the  air-bath,  replace  the  cover,  and 
raise  the  temperature  of  the  bath  until  the  ferric  nitrate  is  decomposed. 
Remove  the  beaker  from  the  air-bath,  allow  it  to  cool,  add  30  c.c.  hydro- 
chloric acid,  and  heat  gradually  until  all  the  ferric  oxide  is  dissolved. 
Remove  the  cover,  and  evaporate  again  to  dryness  in  the  air-bath,  redissolve 
in  30  c.c.  hydrochloric  acid,  dilute  to  about  150  c.c.,  and  filter  on  an  ashless 
filter.  Detach  any  adhering  silica  from  the  sides  and  bottom  of  the  beaker 
with  a  "  policeman,"  or  with  a  piece  of  filter-paper,  and  wash  it  out  with 
cold  water.  Wash  the  filter  first  with  dilute  hydrochloric  acid,  and 
finally  with  water.  Dry,  and  ignite  in  a  platinum  crucible  until  all  the 
carbon  is  burned,  weigh  the  residue  in  the  crucible,  moisten  it  with  water, 
add  from  I  to  10  drops  sulphuric  acid,  and  enough  hydrofluoric  acid  to  dis- 
solve it  completely,  evaporate  to  dryness,  ignite,  and  weigh.  The  difference 


DETERMINATION  OF  SILICON.  73 

between  the  two  weights  is  silica,  which  contains  47.02  per  cent,  of  silicon. 
In  the  absence  of  hydrofluoric  acid,  unless  the  silica  is  perfectly  white,  fuse 
with  5  or  6  times  its  weight  of  sodium  carbonate,  dissolve  in  water, 
acidulate  with  hydrochloric  acid,  evaporate  to  dryness  (in  a  platinum  or 
porcelain  dish,  with  the  arrangement  shown  on  page  20),  redissolve  in 
hydrochloric  acid  and  water,  dilute,  filter,  wash,  ignite,  and  weigh.  When 
the  weight  of  sodium  carbonate  taken  does  not  exceed  2  or  3  grammes, 
allow  the  crucible  to  cool  after  fusion,  and  then  add  to  it  gradually  an 
excess  of  strong  sulphuric  acid,  heating  very  slowly,  until  the  mass  is 
quite  liquid  and  fumes  of  sulphuric  anhydride  come  off.  Allow  it  to  cool, 
dissolve  in  water,  filter,  wash  well,  ignite,  and  weigh. 

By  Solution  in  Nitric  and  Sulphuric  Acids. 

Drown  *  has  suggested  a  method  which,  for  pig-irons,  has  come  into 
very  general  use,  and  which  is  much  more  rapid  than  the  other  method 
and  quite  as  exact.  Treat  I  gramme  of  borings  in  a  platinum  or  porcelain 
dish  with  20  c.c.  nitric  acid,  1.2  sp.  gr.  When  all  action  has  ceased,  add 
20  c.c.  of  sulphuric  acid  (equal  parts  of  acid  and  water),  and  evaporate — 
using  the  arrangement  shown  on  page  20 — -until  copious  fumes  of  sul- 
phuric anhydride  are  given  off.  Allow  to  cool,  and  dilute  with  150  c.c. 
water;  heat  carefully  until  all  the  ferric  sulphate  has  dissolved,  filter  hot,f 
wash  first  with  dilute  hydrochloric  acid,  i.i  sp.  gr.,  and  then  with  hot 
water,  ignite,  and  weigh.  Treat  the  contents  of  the  crucible  with  sulphuric 
and  hydrofluoric  acids,  evaporate  to  dryness,  ignite,  and  weigh  again.  The 
difference  between  the  two  weights  is  silica. 

By  Volatilization  in  a  Current  of  Chlorine  Gas. 

As  almost  all  steels  and  irons  contain  slags  of  various  compositions, 
it  must  be  understood  that  the  silica  obtained  by  the  methods  given 
above  is  the  total  silica,  comprising  any  silica  that  may  be  present  in 

*  Journal  Inst.  Min.  Engineers,  vii.  346. 

f  Dr.  Dudley  has  shown  that  upon  long  standing  silica  dissolves,  and  it  is  therefore  advisable  to 
filter  the  sulphuric  acid  solution  as  soon  as  the  ferric  sulphate  is  dissolved. 


ANAL  YSIS   OF  IRON  AND   STEEL. 


DETERMINATIOAT  OF  SILICON.  75 

the  admixed  slag,  as  well  as  that  formed  from  the  silicon  present  in 
the  metal.  The  volatilization  method  separates  the  two.  The  process 
suggested  by  Drown,*  and  worked  out  independently  two  years  later 
by  Watts,f  is  as  follows.  Fig.  49  shows  the  general  arrangement  of 
the  apparatus.  The  large  flask  contains  strong  common  manganese 
dioxide  in  lumps.  The  bottle  above  it  contains  strong  common  hydro- 
chloric acid,  which  runs  into  the  flask  through  a  siphon-tube  extending 
almost  to  the  bottom.  The  flask  stands  in  a  dish  containing  water, 
which  can  be  heated  by  the  burner  under  the  tripod.  The  evolution- 
tube  from  the  flask  has  a  stopcock,  and  connects  with  the  three  bulb- 
tubes  on  the  stand,  the  first  containing  water,  the  second  pumice-stone, 
and  the  third  pumice  saturated  with  strong  sulphuric  acid.  The 
outlet-tube  from  the  latter  leads  into  the  porcelain  or  glass  tube  in 
the  furnace.  This  tube  contains  small  lumps  of  charcoal  or  gas 
carbon,  kept  in  position  by  loosely  fitting  plugs  of  asbestos,  and 
occupying  about  8  inches  (200  mm.)  in  the  middle  of  the  tube. 
The  outlet-tube  from  this  connects  with  the  drying-tubes  on  the 
second  stand,  which  contain  pumice  moistened  with  strong  sulphuric 
acid.  The  outlet  from  the  second  drying-tube  connects  with  the  glass 
combustion-tube,  which  leads  through  the  second  furnace,  and  is  bent 
at  a  right  angle  where  it  is  connected  with  the  large  tubes,  half  filled 
with  water.  The  apparatus  being  in  order,  \  start  a  slow  current  of 
chlorine  through  the  apparatus  by  blowing  hydrochloric  acid  from  the 
bottle  into  the  flask  and  filling  the  dish  in  which  the  latter  stands 
with  water.  Light  a  low  light  under  the  dish,  and  open  the  stopcock 
wide  enough  to  allow  a  very  slow  current  to  bubble  through  the 
bulbs.  Light  the  burners  of  the  first  furnace  so  that  the  tube  is 
heated  to  dull  redness.  When  the  apparatus  is  full  of  chlorine,  place 
i  gramme  of  pig-iron,  or  3  grammes  of  steel,  in  a  porcelain  boat 
about  3  inches  long,  distributing  the  drillings  evenly  along  the  "bottom 

*  Jour.   Inst.   Min.    Engineers,   viii.   508.  f  Chem.   News,  xlv.    279. 

\  All  the  stoppers  used  should  be  of  rubber  coated  with  paraffine  on  the  ends,  or  of  asbestos, 
and  where  glass  tubes  are  joined  together  with  rubber  the  ends  of  the  glass  tubes  should  be 
brought  into  close  contact. 


76  ANAL  YSIS   OF  IRON  AND   STEEL. 

of  the  boat.  Remove  the  stopper  at  the  rear  end  of  the  second  tube 
and  insert  the  boat  to  about  the  centre.  Replace  the  stopper,  and 
continue  the  current  of  chlorine  in  the  cold  for  ten  or  fifteen  minutes 
to  make  sure  that  no  oxygen  remains  in  the  tube,  then  light  the  burner 
under  the  forward  end  of  the  boat.  The  heat  must  be  just  sufficient 
to  volatilize  the  ferric  chloride,  which  should  condense  in  the  cooler 
part  of  the  tube,  and  the  current  of  gas  should  be  slow  enough  to  pre- 
vent any  ferric  chloride  from  being  carried  forward  into  the  water-tubes 
or  any  loss  of  carbon  from  the  boat.  When  the  fumes  of  ferric  chlo- 
ride begin  to  come  off  more  slowly,  light  the  next  burner,  and  con- 
tinue until  all  the  burners  under  the  boat  are  lighted,  maintaining  the 
heat  until  the  fumes  of  ferric  chloride  cease.  The  tube  for  the  entire 
length  occupied  by  the  boat  should  be  at  a  dull  red  heat.  Should 
the  condensed  ferric  chloride  at  any  time  choke  the  tube  so  as  to 
prevent  the  passage  of  the  gas,  heat  that  part  of  the  tube  gently  with 
a  spirit-lamp,  so  as  to  drive  the  ferric  chloride  a  little  farther  along 
the  tube.  When  the  fumes  of  ferric  chloride  are  no  longer  given  off 
from  the  boat,  the  operation  may  be  considered  finished.  Turn  out 
the  lights  under  the  tube  containing  the  boat,  remove  the  stopper, 
and  draw  out  the  boat,  which  now  contains  the  carbon,  the  slag,  and 
the  greater  part  of  the  manganese  (as  chloride)  which  were  contained 
in  the  iron  and  steel.  This  residue  may  be  used  for  the  determination 
of  the  carbon  or  the  slag,  as  will  be  shown  farther  on.  If  another 
determination  is  to  be  made,  another  tube  may  be  substituted  for  the 
one  which  contained  the  boat,  and  the  analysis  carried  out  in  the 
manner  described  above.  If  not,  put  out  all  the  lights,  close  the 
stopcock,  and  withdraw  the  combustion-tube  with  the  water-tubes. 
Remove  the  stoppers  from  the  latter,  and  pour  the  contents  of  these 
tubes  into  a  platinum  dish  containing  a  small  amount  of  an  aqueous 
solution  of  sulphurous  acid,  to  prevent  the  chlorine  in  the  solutions 
from  acting  on  the  platinum.  Rinse  the  tubes  into  the  dish,  and  if 
any  silica  has  separated  and  adheres  to  the  water-tubes  or  to  the  end 
of  the  combustion-tube,  loosen  it  with  a  "  policeman"  and  wash  it  into 
the  dish.  Add  5  c.c.  strong  sulphuric  acid,  evaporate  to  dryness,  and 


DETERMINATION  OF  SILICON.  77 

heat  until  fumes  of  sulphuric  anhydride  are  given  off.  Allow  the  dish 
to  cool,  add  100  c.c.  cold  water,  and  filter  the  silica  on  a  small  ashless 
filter.  Burn  and  weigh  as  silica.  Calculate  to  Silicon.  The  filtrate 
from  the  silica  will  contain  any  titanic  acid  which  may  have  been  in 
the  metal  and  which  can  be  determined,  as  will  be  shown  farther  on. 
Silicon  and  titanium  are  volatilized  as  chlorides,  under  the  conditions 
shown  above,  and  decomposed  by  water  thus:  SiCl4  -(-  2H2O  =  ^HC1  -f 
SiO2  and  TiCl4  +  2H2O  =  4HC1  +TiO2. 


Rapid  Method  for  Determination  of  Silicon.      (S.  Alfred  Ford.*) 

At  the  Edgar  Thomson  Steel-Works  the  molten  pig-metal  is  taken 
directly  from  the  furnaces  to  the  converters,  and  it  is  generally  necessary 
to  determine  the  amount  of  silicon  in  the  pig-iron  as  a  guide  in  blowing 
the  metal.  To  get  the  sample  for  analysis,  a  small  ladle  is  dipped  into  the 
iron  as  it  runs  from  the  furnace,  and  a  small  quantity  of  molten  iron  is 
taken.  The  ladle  is  then  held  about  three  feet  above  a  bucket  of  water, 
and  the  molten  metal  dropped  into  the  water,  at  the  same  time  giving  the 
ladle  a  circular  motion  over  the  bucket.  This  will  cause  the  iron  to  form 
in  globules,  more  or  less  round  according  to  the  amount  of  silicon  con- 
tained in  the  iron.  Thus,  with  iron  which  contains  2  per  cent,  of  silicon 
or  more,  the  globules  will  be  almost  perfectly  round,  concave  on  the  upper 
surface,  and  generally  from  J^  inch  (6  mm.)  to  ^  inch  (9  mm.)  in  diameter; 
while  if  the  iron  be  low  in  silicon,  the  shot  or  drops  will  be  very  small,  flat, 
and  irregular  in  shape,  and  if  the  iron  be  very  low  in  silicon,  as  is  the  case 
with  spiegel  and  ferro-manganese,  the  shot  will  be  elongated  and  have  tails 
sometimes  ^  inch  (6  mm.)  in  length.  In  fact,  a  close  observer  can  soon 
judge  very  closely  as  to  the  amount  of  silicon  from  the  condition  of  these 
shot  or  drops.  The  next  step  in  the  process  is  to  take  the  shot  from  the 
bucket  and  place  them  for  a  minute  in  the  ladle  which  has  been  used  to 
dip  up  the  molten  iron.  The  ladle,  being  hot,  will  dry  the  shot  almost 
instantly.  The  shot  are  then  placed  in  a  large  steel  mortar  (Fig.  7,  page 
17)  and  crushed.  The  crushed  shot  are  then  sifted  with  a  fine  sieve,  and 

*  Prepared  by  Mr.   Ford  for  this  volume. 


78  ANALYSIS   OF  IRON  AND   STEEL. 

.5  gramme  of  the  fine  sittings  are  placed  in  a  platinum  evaporating-dish, 
10  c.c.  hydrochloric  acid,  1.2  sp.  gr.,  are  then  added,  and  the  dish  covered 
with  a  watch-glass.  The  dish  is  then  placed  over  a  light,  and  the  iron 
dissolved ;  as  soon  as  solution  takes  place,  which  requires  about  one 
minute,  as  the  particles  of  iron  are  so  small,  the  watch-glass  is  removed 
and  the  solution  evaporated  to  dryness  as  rapidly  as  possible  over  a  naked 
light;  as  soon  as  dry,  not  even  waiting  for  the  dish  to  cool,  dilute  hydro- 
chloric acid  is  dropped  on  the  ferric  chloride,  and  as  soon  as  all  the  ferric 
oxide  (which  may  have  been  formed  by  the  decomposition  of  the  chloride) 
is  dissolved,  water  is  added.  The  contents  of  the  dish  are  then  poured 
on  a  filter,  to  which  is  attached  a  pump,  filtered,  and  washed.  The  filter 
and  its  contents  are  then  placed  in  a  weighed  platinum  crucible,  placed 
over  a  blast-lamp  ;  as  soon  as  the  filter-paper  is  burned  off,  the  crucible 
is  turned  on  its  side,  the  lid  removed,  and  a  small  jet  of  oxygen  is  driven 
very  gently  into  the  crucible.  As  soon  as  what  little  carbon  there  is  in 
the  precipitate  is  burned  off,  the  crucible  is  cooled  and  weighed,  and  the 
amount  of  silicon  calculated  from  the  weight  of  the  silica  in  the  crucible. 

By  this  method  the  amount  of  silicon  in  a  pig-iron  can  be  determined 
in  twelve  minutes  from  the  time  the  ladle  is  put  into  the  molten  iron,  and 
it  gives  results  close  enough  for  practical  purposes. 


DETERMINATION    OF   SLAG   AND    OXIDES. 

A  certain  amount  of  slag  and  oxide  of  iron  is  always  present  in 
puddled  iron  as  a  mechanical  admixture.  It  is  also  found,  as  a  general 
thing,  in  basic  steel,  and  the  presence  of  slag  in  steel  made  by  the  acid 
process,  as  well  as  in  pig-iron,  is  not  unusual.  The  easiest  method  for  the 
determination  of  these  substances  is  by  solution  in  iodine,  as  suggested 
by  Eggertz. 

By  Solution  in  Iodine. 

Place  5  grammes  of  borings  free  from  lumps  in  a  No.  2  Griffin's  beaker. 
Stand  the  beaker,  carefully  covered  with  a  watch-glass,  in  a  dish  filled 
with  scraped  ice  or  snow,  so  that  the  bottom  and  sides  of  the  beaker 
half-way  up  shall  be  in  contact  with  it.  Pour  over  the  iron  in  the  beaker 


OF  THF 
UNIVERSITY 

or 


DETERMINATION  OF  SLAG   AND    OXIDES. 

25  c.c.  of  ice-cold  boiled  water,  and  stir  until  all  the  air  in  the  borings  has 
escaped.  Add  gradually  from  28  to  30  grammes  of  resublimed  iodine,* 
stirring  occasionally,  until  all  the  iodine  has  dissolved.  Keep  the  beaker 
constantly  surrounded  by  ice,  and  add  the  iodine  slowly  enough  to  prevent 
any  rise  in  the  temperature  of  the  solution.  Stir  the  solution  frequently 
until  the  iron  is  perfectly  dissolved,  which  will  take  several  hours  ;  then 
add  100  c.c.  cold  boiled  water,  allow  the  insoluble  matter  to  settle,  and 
decant  the  supernatant  fluid  on  a  small  ashless  filter.  Wash  the  insoluble 
matter  several  times,  by  decantation,  with  cold  water,  then  add  to  it  a  little 
water,  with  a  few  drops  of  hydrochloric  acid,  and  observe  whether  any 
hydrogen  is  disengaged.  If  none  can  be  perceived,  the  metallic  iron  may 
be  considered  entirely  dissolved  ;  but  if  gas  is  given  off,  the  opposite  is  the 
case.  In  either  event,  quickly  decant  the  acidulated  water  on  the  filter,  and 
if  any  metallic  iron  remains,  add  a  very  little  water  and  some  iodine  to  dis- 
solve the  iron  entirely.  Then  transfer  the  insoluble  matter,  consisting  of 
graphite,  carbonaceous  matter,  slag,  iron  oxide,  and  some  silica,  to  the 
filter,  wash  the  filter  once  with  very  dilute  hydrochloric  acid  (i  acid  to  20 
water),  and  finally  with  cold  water,  until  the  filtrate  is  free  from  iron.  Un- 
fold the  filter,  and  with  a  fine  jet  wash  off  the  insoluble  matter  into  a  small 
platinum  or  silver  dish.  Evaporate  almost  to  dryness,  add  50  c.c.  solution 
of  caustic  potash,  sp.  gr.  i.i,  and  boil  five  or  ten  minutes.  Decant  the 
liquid  on  a  very  small  ashless  filter,  repeat  the  boiling  with  fresh  caustic 
potash,  transfer  the  insoluble  matter  to  the  filter,  and  wash  well  with  hot 
water.  Wash  once  with  dilute  hydrochloric  acid  (i  acid  to  20  water),  and 
finally  with  hot  water,  until  the  filtrate  gives  no  precipitate  with  a  solution 
of  silver  nitrate.  Dry,  ignite,  and  weigh  as  Slag  and  Iron  Oxide. 

Instead  of  using  iodine  directly  for  the  solution  of  the  iron,  a  solution 
of  iodine  in  iron  iodide,  as  suggested  by  Eggertz,f  may  be  used  to  great 
advantage,  as  it  affords  a  ready  method  for  getting  rid  of  the  impurities 
usually  present  in  resublimed  iodine.  Treat  5  grammes  of  iron  (as  free  as 
possible  from  silicon)  with  25  grammes  of  iodine,  and,  when  the  solution 
is  complete,  add  30  grammes  more  of  iodine,  which  will  dissolve  in  the 

*  Page  41.  f  Jern-Kontorets  Annaler,  1881,  p.  301,  and  Chem.  News,  xliv.  173. 


80  ANAL  YSIS   OF  IRON  AND   STEEL. 

iron  iodide  in  a  few  minutes.  Dilute  to  50  c.c.  with  cold  boiled  water  and 
filter  through  a  washed  filter.  Add  the  filtrate  at  once  to  5  grammes  of 
the  weighed  sample,  and,  after  solution  is  complete,  proceed  as  directed 
above. 

By  Volatilization  in  a  Current  of  Chlorine  Gas. 
Proceed  exactly  as  in  the  method  for  the  determination  of  silicon 
(pages  73  et  seg.)  until  the  boat  is  withdrawn  from  the  combustion-tube. 
Wash  the  contents  of  the  boat  into  a  small  beaker  with  a  jet  of  cold 
water,  and  filter  on  a  small  ashless  filter.  The  water  dissolves  any  soluble 
metallic  chlorides  which  are  not  volatile  at  a  low  red  heat,  and  the  in- 
soluble matter  in  the  filter  consists  of  slag  and  carbon.  Burn  off  the 
carbon  and  weigh  the  residue  as  Slag  and  Oxides.  Or,  if  the  carbon  has 
been  determined  by  another  operation,  filter  the  carbon  and  slag  on  a 
counterpoised  filter  *  or  on  a  Gooch  crucible,  dry  at  100°  C.,  and  weigh  as 
Carbon,  Slag,  and  Oxides ;  by  subtracting  the  weight  of  the  carbon  the 
difference  is  Slag  and  Oxides. 


DETERMINATION    OF    PHOSPHORUS. 

For  the  determination  of  phosphorus  in  iron  and  steel  but  two  methods 
are  in  general  use,  either  of  which,  properly  carried  out,  will  give  ex- 
tremely accurate  results.  Some  chemists  prefer  one  method,  some  the 
other,  while  a  combination  of  the  two  is  sometimes  used.  The  two 
general  methods  are  known  respectively  as  the  Acetate  Method  and  the 
Molybdate  Method.  There  are  innumerable  variations  in  the  details, 
especially  of  the  latter  method,  but  any  departure  from  what  might  be 
termed  the  standard  instructions  should  never  be  attempted  by  any  but  a 
very  experienced  analyst. 

The  Acetate  Method. 

The  essential  parts  of  this  method  were  suggested  by  Fresenius,f  the 
changes  and  improvements  in  details  being  the  work  of  many  chemists. J 

*  See  page  28.  f  Jour,  fur  Pr.  Ch.,  xlv.  258. 

J  Tenth  Census  of  the   U.  S.,  vol.  xv.     "  Iron  Ores  of  the  U.  S.,"  p.  523. 


DETERMINATION  OF  PHOSPHORUS.  8 1 

Treat  5  grammes  of  drillings  in  a  No.  4  Griffin's  beaker  with  80  c.c. 
nitric  acid  (1.2  sp.  gr.),  and,  when  violent  action  has  ceased,  add  10  c.c. 
strong  hydrochloric  acid.  Evaporate  the  solution  to  dryness  in  the  air- 
bath,  replace  the  cover,  and  heat  until  the  ferric  nitrate  is  nearly  all  decom- 
posed. Cool,  add  30  c.c.  hydrochloric  acid,  heat  gradually  until  the  iron 
oxide  is  dissolved,  and  evaporate  to  dryness  again  in  the  air-bath.  Cool, 
dissolve  in  30  c.c  hydrochloric  acid,  dilute,  and,  in  steels  or  puddled  iron, 
when  silicon  is  to  be  determined,  filter,  and  treat  the  insoluble  matter  as 
directed  for  the  determination  of  silicon,  on  page  72. 

In  the  case  of  pig-irons  which  may  contain  titanium,  filter,  and  keep 
the  residue  of  graphite,  silica,  etc.,  for  treatment,  as  directed  farther  on, 
"  when  titanium  is  present." 

In  the  case  of  steels,  when  silicon  is  not  to  be  determined  in  this  portion, 
the  solution  need  not  be  filtered  at  all,  but  may  be  diluted  at  once  to 
about  250  c.c. 

In  any  case,  heat  the  filtered  or  unfiltered  hydrochloric  acid  solution 
nearly  to  boiling,  remove  the  beaker  from  the  light,  and  add  gradually  from 
a  small  beaker  a  mixture  of  10  c.c.  acid  ammonium  sulphite  *  and  20  c.c. 
ammonia,  stirring  constantly.  The  precipitate,  which  forms  at  first,  re- 
dissolves,  and  when  all  but  about  2  or  3  c.c.  of  the  acid  ammonium  sulphite 
solution  has  been  added,  replace  the  beaker  over  the  light.  If  at  any  time 
while  adding  the  acid  ammonium  sulphite  solution  the  precipitate  formed 
will  not  redissolve  even  after  vigorous  stirring,  add  a  few  drops  of  hydro- 
chloric acid,  and,  when  the  solution  clears,  continue  the  addition,  very 
slowly,  of  the  acid  ammonium  sulphite.  After  replacing  the  beaker  on  the 
light,  add  to  the  solution  (which  should  smell  quite  strongly  of  sulphurous 
anhydride)  ammonia,  drop  by  drop,  until  the  solution  is  quite  decolorized, 
and  until  finally  a  slight  greenish  precipitate  remains  undissolved  even  after 
vigorous  stirring.  Now  add  the  remaining  2  or  3  c.c.  of  the  acid  ammonium 
sulphite  solution,  which  should  throw  down  a  white  precipitate,  which 
usually  redissolves,  leaving  the  solution  quite  clear  and  almost  perfectly 
decolorized.  Should  any  precipitate  remain  undissolved,  however,  add 

*  See  page  44. 

6 


82  ANAL  YSIS   OF  IRON  AND   STEEL. 

hydrochloric  acid,  drop  by  drop,  until  the  solution  clears,  when  it  should 
smell  perceptibly  of  sulphurous  anhydride.  If  the  reagents  are  used  in 
exactly  the  proportions  indicated,  the  reactions  will  take  place  as  described, 
and  the  operations  will  be  readily  and  quickly  carried  out.  If  the  solu- 
tion of  acid  ammonium  sulphite  is  weaker  than  it  should  be,  of  course  the 
ferric  chloride  will  not  be  reduced,  and  the  solution,  at  the  end  of  the 
operation  described  above,  will  not  be  decolorized  and  will  not  smell 
of  sulphurous  anhydride.  In  this  case  add  more  acid  ammonium  sulphite 
(without  the  addition  of  ammonia)  until  the  solution  smells  strongly  of 
sulphurous  anhydride,  then  add  ammonia  until  the  slight  permanent 
precipitate  appears,  and  redissolve  it  in  as  few  drops  of  hydrochloric  acid 
as  possible.  The  solution  being  now  very  nearly  neutral,  the  iron  in 
the  ferrous  condition,  and  an  excess  of  sulphurous  acid  present,  add  to 
the  solution  5  c.c.  of  hydrochloric  acid  to  make  it  decidedly  acid  and  to 
insure  the  complete  decomposition  of  any  excess  of  the  acid  ammonium 
sulphite  which  may  be  present.  Boil  the  solution,*  while  a  stream  of 
carbonic  acid  passes  through  it,  until  every  trace  of  sulphurous  anhydride 
is  expelled,  then  pass  a  current  of  hydrogen  suphide  through  it  for  about 
fifteen  minutes  to  precipitate  any  arsenic  which  may  be  present,  and  finally 
allow  the  solution  to  stand  in  a  warm  place  until  the  smell  of  hydrogen 
sulphide  has  disappeared,  or,  better,  pass  a  current  of  carbonic  acid 
through  the  solution,  which  will  expel  the  hydrogen  sulphide  in  a  few 
minutes.  The  arrangement,  Fig.  50,  is  convenient  for  this  purpose.  Filter 
from  any  arsenious  sulphide,  cuprous  sulphide,  sulphur,  etc.,  into  a  No.  5 
beaker,  wash  with  cold  water,  and  to  the  filtrate  add  a  few  drops  of 
bromine-water,  or  of  a  solution  of  ferric  chloride,  and  cool  it  by  placing 
the  beaker  in  cold  water.  To  the  cold  solution  add  ammonia  from  a 
small  beaker  very  slowly,  and  finally,  drop  by  drop,  with  constant  stirring. 
The  green  precipitate  of  ferrous  hydrate  which  forms  at  first  is  dissolved 
by  stirring,  leaving  the  solution  perfectly  clear,  but  subsequently,  although 
the  green  precipitate  dissolves,  a  whitish  one  remains,  and  the  next  drop 

*  By  passing  a  current  of  carbonic  acid  through  the  boiling  solution  the  sulphurous  anhydride  is 
soon  expelled,  and  the  operation  requires  no  watching. 


DETERMINATION  OF  PHOSPHORUS.  83 

of  ammonia  increases  the  whitish  precipitate  or  gives  it  a  reddish  tint,  and 
finally  the  greenish  precipitate  remains  undissolved  even  after  vigorous 
stirring,  and  another  drop  of  ammonia  makes  the  whole  precipitate  appear 
green.  If  before  this  occurs  the  precipitate  does  not  appear  decidedly  red 
in  color,  dissolve  the  green  precipitate  by  a  drop  or  two  of  hydrochloric 

FIG.  50. 


acid,  and  add  a  little  bromine-water  or  ferric  chloride  solution  (i  or  2  c.c.), 
then  add  ammonia  as  before,  and  repeat  this  until  the  reddish  precipitate 
is  obtained,  and  then  the  green  coloration  as  described  above.  Dissolve 
this  green  precipitate  in  a  very  few  drops  of  acetic  acid  (sp.  gr.  1.04), 
when  the  precipitate  remaining  will  be  quite  red  in  color,  then  add  about 


84  ANAL  YSIS   OF  IRON  AND   STEEL. 

I  c.c.  of  acetic  acid,  and  dilute  the  solution  with  boiling  water,  so  that  the 
beaker  may  be  about  four-fifths  full.  Heat  to  boiling,  and  when  the 
solution  has  boiled  one  minute,  lower  the  light,  filter  as  rapidly  as  possible 
through  a  5^-inch  (i4O-mm.)  filter,  and  wash  once  with  hot  water.  The 
filtrate  should  run  through  clear,  but  in  a  few  minutes  it  will  appear  cloudy 
by  the  precipitation  of  the  ferric  oxide,  which  has  been  formed  by  the 
exposure  of  the  filtered  solution  to  the  air.  The  points  to  be  observed 
are  the  red  color  of  the  precipitate  and  the  clearness  of  the  solution  when 
it  first  runs  through.  Ferric  phosphate  being  white,  the  red  color  of  the 
precipitate  shows  that  enough  ferric  salt  was  present  in  the  solution  to  form 
ferric  phosphate  with  all  the  phosphoric  acid,  and  enough  more  to  color 
the  ferric  phosphate  red  with  the  excess  of  ferric  oxide. 

When  the  precipitate  has  drained  quite  dry,  pour  about  15  c.c.  of 
hydrochloric  acid  into  the  beaker  in  which  the  precipitation  was  made, 
warm  it  slightly  so  that  the  acid  may  condense  on  the  sides  and  dissolve 
any  adhering  oxide,  wash  off  the  cover  into  the  beaker,  add  about  10  c.c. 
of  bromine- water,  pour  this  on  the  filter  containing  the  precipitate,  allowing 
it  to  run  around  the  edge  of  the  filter,  and  let  the  solution  run  into  a  No.  I 
Griffin's  beaker.  Wash  out  the  beaker  once  or  twice,  and  then  wash  the 
filter  well  with  hot  water.  If  the  acid  in  the  beaker  is  not  sufficient  to 
dissolve  the  precipitate  completely,  drop  a  little  strong  acid  around  the 
edge  of  the  filter  before  washing  it  with  hot  water.  The  scaly  film  of 
difficultly  soluble  oxide  which  sometimes  forms  on  boiling  the  acetate 
precipitate  is  caused  by  the  presence  of  too  much  ammonium  acetate,  but 
when  the  instructions  given  above  are  carefully  carried  out  it  never  appears. 
Evaporate  the  solution  in  the  small  beaker  nearly  to  dryness  to  get  rid  of 
the  excess  of  hydrochloric  acid,  add  to  it  a  filtered  solution  of  5  or  10 
grammes  of  citric  acid  (according  to  the  size  of  the  precipitate  of  ferric 
oxide,  etc.)  dissolved  in  from  loto  20  c.c.  of  water,  then  from  5  to  10  c.c.  of 
magnesia-mixture  and  enough  ammonia  to  make  the  solution  faintly  alka- 
line. Stand  the  beaker  in  cold  water,  and  when  the  solution  is  perfectly 
cold,  add  to  it  one-half  its  volume  of  strong  ammonia  and  stir  it  well. 
When  the  precipitate  of  ammonium-magnesium  orthophosphate  has  begun 
to  form,  stop  stirring,  and  allow  it  to  stand  in  cold  water  for  ten  or  fifteen 


DETERMINATION  OF  PHOSPHORUS.  85 

minutes,  then  stir  vigorously  several  times  at  intervals  of  a  few  minutes, 
and  allow  it  to  stand  overnight.  Filter  on  a  small  ashless  filter,  and  wash 
with  a  mixture  of  2  parts  of  water  and  I  part  of  ammonia  containing  2.5 
grammes  of  ammonium  nitrate  to  100  c.c. 

Dry  the  filter  and  precipitate,  and  ignite  them  at  a  very  low  temperature 
at  first  so  as  to  carbonize  the  filter  without  decomposing  the  precipitate, 
which  may  then  readily  be  broken  up  with  a  platinum  wire.  Raise  the 
heat  gradually,  and  finally  ignite  at  the  highest  temperature  of  the  Bunsen 
burner.  When  the  precipitate  is  perfectly  white,  cool  and  weigh.  Then 
fill  the  crucible  half  full  of  hot  water,  add  from  5  to  20  drops  of  hydro- 
chloric acid,  and  heat  until  the  precipitate  has  dissolved.  Filter  off  on 
another  small,  ashless  filter  any  silica  or  ferric  oxide  that  may  remain, 
ignite,  and  weigh.  The  difference  between  the  two  weights  is  the  weight  of 
magnesium  pyrophosphate,  which,  multiplied  by  0.27836,  gives  the  weight 
of  phosphorus. 

When   Titanium  is  Present. 

When  a  solution  of  ferric  chloride  containing  titanic  and  phosphoric 
acids  is  evaporated  to  dryness,  a  compound  of  titanic  acid,  phosphoric 
acid,  and  ferric  oxide  is  formed,  completely  insoluble  in  dilute  hydro- 
chloric acid.* 

Iron  ores  and  pig-irons  containing  titanic  acid  require,  therefore,  a 
somewhat  different  method  of  treatment  from  that  given  above. 

Dry  and  ignite  the  residue  of  graphite,  silica,  etc.,  from  the  solution  of 
the  pig-iron,  so  as  to  burn  off  all  the  carbon.  Moisten  this  residue  with  cold 
water,  add  from  5  to  10  drops  of  sulphuric  acid  and  enough  hydrofluoric 
acid  to  dissolve  the  silica,  and  evaporate  until  fumes  of  sulphuric  anhydride 
are  given  off.  While  this  is  going  on,  proceed  with  the  deoxidation  of  the 
filtrate  as  described  above,  but  when  the  sulphurous  acid  has  been  driven 
off  do  not  pass  hydrogen  sulphide  through  the  solution,  but  cool  it,  and 
proceed  with  the  acetate  precipitation.  Instead  of  dissolving  the  precipi- 
tate, after  washing  it  as  described  above,  dry  the  filter  and  precipitate  in 

*  Published  in  Report  on  Methods  employed  in  the  Analysis  of  the  "Iron  Ores,"  Tenth 
Census  U.  S.,  xv.  512.  I  first  noted  this  fact  in  1878. 


86  ANAL  YSIS   OF  IRON  AND   STEEL, 

the  funnel,  being  careful  not  to  heat  it  so  as  to  scorch  the  filter.  Clean  out 
any  of  the  precipitate  which  may  have  adhered  to  the  sides  of  the  beaker 
in  which  the  precipitation  was  made,  by  wiping  it  with  filter-paper,  and  dry 
this  paper  with  the  filter  and  precipitate. 

When  the  precipitate  is  quite  dry,  transfer  to  a  small  porcelain  mortar. 
The  precipitate  may  readily  be  detached  from  the  filter  by  rubbing  the  sides 
of  the  latter  together  over  a  large  piece  of  white,  glazed  paper,  so  that  any 
little  particles  that  fall  out  may  be  seen.  Roll  up  the  filter  with  the  bits  of 
paper  which  were  used  to  wipe  out  the  beaker,  wrap  a  piece  of  platinum  wire 
around  it,  burn  it  on  the  lid  of  the  crucible  in  which  the  graphite  residue 
was  treated,  and  transfer  the  ash  to  the  mortar.  Grind  the  precipitate  and 
ash  with  from  3  to  5  grammes  of  sodium  carbonate  and  a  little  sodium 
nitrate,  and  transfer  it  to  the  crucible  containing  the  residue  which  was 
treated  by  hydrofluoric  and  sulphuric  acids.  Clean  the  mortar  and 
pestle  by  grinding  a  little  more  sodium  carbonate,  and  add  this  to  the 
other  portion  in  the  crucible.  Fuse  the  whole  for  half  an  hour  or 
more,  cool,  dissolve  the  fused  mass  in  hot  water,  filter  from  the  in- 
soluble ferric  oxide,  etc.,*  acidulate  the  filtrate  with  hydrochloric  acid, 
add  a  few  drops  of  acid  ammonium  sulphite,  boil  off*  all  smell  of 
sulphurous  acid,  and  pass  hydrogen  sulphide  through  the  hot  solution 
to  precipitate  any  arsenic  that  may  be  present.  Pass  a  current  of 
carbonic  acid  through  the  solution  to  expel  the  excess  of  hydrogen 
sulphide,  filter  off  the  arsenious  sulphide,  and  to  the  filtrate  add  a 
sufficient  amount  of  ferric  chloride  solution  to  combine  with  all  the 
phosphoric  acid  as  ferric  phosphate  and  leave  a  slight  excess.  Add 
a  slight  excess  of  ammonia,  which  should  throw  down  a  red  precipi- 
tate, while  the  solution  is  alkaline  to  test-paper;  then  add  acetic  acid 
to  slightly  acid  reaction,  boil,  filter  off  the  ferric  phosphate  and  ferric 
oxide,  and  wash  with  hot  water.  Dissolve  the  precipitate  in  hydro- 
chloric acid,  allow  the  solution  to  run  into  a  small  beaker,  evaporate 
until  the  solution  is  syrupy,  add  citric  acid  and  magnesia-mixture, 


*  This  ferric  oxide,  etc.,  contains  all  the  titanium  that  was  in  the  pig-iron  as  titanate  of  soda, 
and  must  be  kept  for  the  estimation  of  that  element  when  it  is  to  be  determined. 


DETERMINATION  OF  PHOSPHORUS.  8/ 

and  precipitate  the  ammonium-magnesium  orthophosphate  as  described 
above.  Unless  the  amount  of  phosphorus  is  very  small,  a  second 
fusion  of  the  insoluble  residue  of  ferric  oxide,  etc.,  is  necessary.  The 
two  filtrates  can  then  be  added  together,  acidulated  with  hydrochloric 
acid,  and  the  remainder  of  the  process  carried  out  as  directed  above. 
To  avoid  the  fusion  of  the  acetate  precipitate  with  sodium  carbonate, 
which  is  always  troublesome,  the  method  for  the  determination  of 
phosphorus  may  be  modified  (in  many  cases  with  advantage,  and 
generally  when  titanium  is  not  to  be  estimated)  as  follows : 

After  filtering  off  the  insoluble  matter, — graphite,  silica,  etc., — ignite 
it,  burn  off  the  graphite,  and  treat  the  residue  with  hydrofluoric  and 
sulphuric  acids,  evaporate  down  until  the  excess  of  sulphuric  acid  is 
driven  off,  and  fuse  with  sodium  carbonate.  Treat  the  fused  mass 
with  water,  and  filter.  Acidulate  the  filtrate  with  hydrochloric  acid, 
and  add  it  to  the  main  solution,  which  has  been  deoxidized  in  the 
mean  time  with  acid  ammonium  sulphite.  Expel  the  last  traces  of 
sulphurous  acid  from  the  united  filtrates  by  boiling  and  passing  a 
current  of  carbonic  acid  through  the  solution,  as  previously  directed. 
If  the  solution  remains  clear,  pass  hydrogen  sulphide  through  it,  and 
filter  off  the  precipitated  sulphides.  Cool  the  solution,  and  make  the 
acetate  precipitation  as  directed  on  page  81.  The  only  danger  to  be 
apprehended  now  is  the  tendency  of  titanic  acid  to  separate  out  and 
carry  phosphoric  acid  with  it  when  in  the  evaporation  of  the  hydro- 
chloric acid  solution  of  the  acetate  precipitate  the  liquid  becomes 
concentrated.  To  avoid  this,  the  evaporation  must  be  watched  very 
carefully,  and  citric  acid  added  as  soon  as  the  titanic  acid  begins  to 
separate.  Then,  if  the  separation  has  not  proceeded  too  far,  the 
phosphoric  acid  may  be  precipitated  in  the  usual  way.  If,  however, 
the  separation  of  titanic  acid  is  not  checked  in  time,  proceed  with  the 
evaporation  as  directed  on  page  84,  add  5  c.c.  strong  hydrochloric 
acid,  and  warm  gently.  The  solution  will  nearly  always  clear,  but 
if  it  does  not,  add  citric  acid  and  a  slight  excess  of  ammonia,  and 
filter.  Stand  the  filtrate  aside,  burn  off  and  fuse  the  precipitate  with 
sodium  carbonate,  dissolve  in  water,  filter,  acidulate  the  filtrate  with 


88  ANAL  YSIS   OF  IRON  AND   STEEL. 

hydrochloric  acid,  add  a  little  ferric  chloride  solution,  a  slight  excess 
of  ammonia,  and  acidulate  with  acetic  acid.  Boil,  filter  off  the 
precipitate  of  ferric  phosphate  and  oxide,  dissolve  in  a  little  hydro- 
chloric acid,  allow  the  solution  to  run  into  a  small  beaker,  evaporate 
down,  and  add  it  to  the  ammoniacal  filtrate  from  the  separated  titanic 
acid  obtained  above.  Add  excess  of  magnesia-mixture,  and  precipi- 
tate the  phosphoric  acid  in  the  usual  way.  When  the  solution  becomes 
cloudy  after  deoxidation  with  acid  ammonium  sulphite,  and  remains 
so  after  acidulating  with  hydrochloric  acid,  proceed  as  directed  above, 
but  dry,  and  ignite  the  filter  containing  the  precipitate  by  hydrogen 
sulphide  and  that  on  which  the  acetate  precipitate  was  filtered,  fuse 
with  sodium  carbonate,  treat  with  water,  filter,  acidulate  with  hydro- 
chloric acid,  pass  hydrogen  sulphide  through  the  solution,  filter,  add 
a  little  ferric  chloride  solution,  and  precipitate  by  ammonia  and  acetic 
acid.  Add  the  solution  of  this  precipitate,  after  filtering  it  off,  to 
the  solution  of  the  main  acetate  precipitate,  and  proceed  as  before. 

Instead  of  adding  citric  acid  and  magnesia-mixture  to  the  solution 
of  the  acetate  precipitate,  Fresenius,*  and  afterwards  Spiller,f  advised  the 
method  of  adding  citric  acid,  excess  of  ammonia,  and  ammonium  sulphide, 
filtering  off  the  precipitated  ferric  sulphide,  and,  after  evaporating  to  small 
bulk,  adding  magnesia-mixture  and  ammonia.  When  the  bulk  of  the 
iron  precipitate  is  not  too  great,  this  is  quite  unnecessary,  for  many 
determinations  have  shown  that  with  an  excess  of  magnesia-mixture, 
ammonium-magnesium  orthophosphate  is  absolutely  insoluble  in  both 
ferric-ammonium  citrate  and  ammonium-aluminum  citrate. 

The  precipitate  is  also  insoluble  in  ammonia-water  (i  part  of  ammonia 
to  2  parts  of  water). 

The  Molybdate  Method. 

Svanberg  and  StruveJ  first  discovered  the  reaction  on  which  this 
method  is  based,  and  Sonnenschein  §  first  used  it  quantitatively.  Dissolve 
5  grammes  of  drillings  in  a  No.  4  Griffin's  beaker,  in  80  c.c.  nitric  acid  (1.2 

*  Jour,  fur  Pr.  Chem.,  xlv.  258.  |  Jour-  Chem.  Soc.  (2),  i..  148. 

J  Jour,  fur  Pr.  Chem.,  xliv.  291.  %  Ibid.,  liii.  339. 


DETERMINATION  OF  PHOSPHORUS.  89 

sp.  gr.).  Evaporate  to  dryness  in  the  air-bath,  replace  the  cover,  and  heat 
for  one  hour  at  a  temperature  of  about  200°  C.  in  order  to  decompose  all 
the  carbonaceous  matter,*  otherwise  the  precipitation  of  the  phospho- 
molybdate  will  be  incomplete.  Allow  the  beaker  to  cool,  dissolve  the 
precipitate  in  30  c.c.  hydrochloric  acid,  evaporate  to  dryness  to  render 
the  silica  insoluble,  redissolve  in  30  c.c.  hydrochloric  acid,  and  evaporate 
carefully  until  the  excess  of  hydrochloric  acid  is  driven  off.  Add  30  c.c. 
nitric  acid  and  evaporate  nearly  dry,  add  nitric  acid  again  and  evapo- 
rate to  drive  off  all  the  hydrochloric  acid,  add  from  50  to  100  c.c.  molyb- 
date  solution, f  heat  it  to  40°  C.  in  a  water-bath  carefully  kept  at  this 
temperature,  and  allow  it  to  stand  in  the  bath  for  about  four  hours.  Filter 
on  a  small,  washed  filter,  and  wash  thoroughly  with  dilute  molybdate 
solution  (i  part  of  solution  to  I  part  of  water)  until  a  drop  of  the  filtrate 
gives  no  reaction  for  iron  with  potassium  ferrocyanide.  Stand  the  filtrate 
aside  in  a  warm  place  to  see  whether  any  further  precipitation  of  ammonium 
phospho-molybdate  takes  place  ;  if  it  does,  it  must  be  filtered  off  and  treated 
like  the  main  precipitate.  Pour  2  or  3  c.c.  strong  ammonia  on  the  precipi- 
tate, stir  it  up  with  a  fine  jet  of  hot  water,  and  allow  the  solution  to  run 
into  the  flask  or  beaker  in  which  the  precipitation  of  phospho-molybdate 
was  made.  When  it  has  all  run  through  the  filter,  replace  the  flask  or 
beaker  by  a  small  beaker  of  a  little  over  100  c.c.  capacity,  remove  any 
phospho-molybdate  that  may  have  adhered  to  the  sides  of  the  original 
flask  or  beaker,  by  means  of  the  ammoniacal  filtrate,  and  then  pour  this 
back  on  the  filter  and  allow  it  to  run  through  into  the  small  beaker. 
Wash  out  the  beaker  or  flask  with  hot  water  and  pour  it  on  the  filter  with 
the  addition  of  a  little  more  ammonia.  Unless  the  precipitate  of  phospho- 
molybdate  is  very  large,  this  amount  of  ammonia  should  dissolve  it,  and  a 
very  little  more  washing  should  be  sufficient.  If  the  precipitate  is  very 
large,  it  may  be  necessary  to  use  more  ammonia  and  more  wash-water,  but 
under  all  circumstances  the  amount  of  ammonia  and  of  wash-water  should 
be  as  small  as  is  consistent  with  perfect  solution  of  the  precipitate  and 

*  In  1877  I  discovered  the  necessity  for  destroying  the  carbonaceous  matter,  and  communicated 
the  fact  to  Hunt  and  Peters,  who  mentioned  it  in  the  Metallurgical  Review,  ii.  365. 
f  See  page  59. 


90  ANAL  YSIS   OF  IRON  AND   STEEL. 

thorough  washing  of  the  beaker  and  filter.  When  the  precipitate  is  small, 
the  filtrate  and  washings  should  amount  to  about  25  c.c.  Neutralize  the 
solution  with  strong  hydrochloric  acid ;  if  the  yellow  phospho-molybdate 
begins  to  precipitate,  add  ammonia  until  it  redissolves,  and  if  there  should 
remain  a  flocculent  white  precipitate,  probably  silica,  after  the  solution  is 
quite  alkaline,  filter  it  off.  Then  to  the  cold  alkaline  "liquid  add,  very 
slowly,  10  c.c.  magnesia-mixture,  stirring  constantly,  and  after  the 
magnesia-mixture  is  all  in, -add  one-third  the  volume  of  the  solution  of 
strong  ammonia  and  stir  vigorously.  It  is  well  to  stand  the  beaker  in  cold 
water  and  stir  the  solution  several  times  after  the  precipitate  has  begun  to 
crystallize  out.  After  standing  about  four  hours,  it  may  be  filtered  off  on  a 
very  small  ashless  filter  and  washed  with  dilute  ammonia-water  (i  part 
ammonia,  0.9  sp.  gr.,  to  2  parts  water)  containing  2.5  grammes  ammonium 
nitrate  to  the.  100  c.c.  Dry,  ignite  very  carefully  to  burn  off  the  carbo- 
naceous matter,  and  finally  heat  for  ten  minutes  over  the  blast-lamp  to 
volatilize  any  molybdic  acid  that  may  have  been  precipitated  with  the 
ammonium-magnesium  orthophosphate,  cool,  and  weigh.  Fill  the  crucible 
half  full  of  hot  water,  add  from  5  to  20  drops  hydrochloric  acid,  and  heat 
for  a  few  minutes  to  dissolve  the  magnesium  pyrophosphate.  Pour  the 
contents  of  the  crucible  on  a  small  ashless  filter,  wash,  ignite,  and  weigh 
the  small  residue  that  may  remain  undissolved.  The  difference  between 
the  two  weights  is  the  weight  of  magnesium  pyrophosphate,  which  con- 
tains 27.836  per  cent,  phosphorus. 

Many  chemists,  following  Eggertz,*  prefer  to  weigh  the  yellow  phospho- 
molybdate  direct  instead  of  dissolving  it  and  precipitating  as  ammonium- 
magnesium  orthophosphate.  In  this  event  take  I  gramme  of  the  drill- 
ings and  proceed  exactly  as  directed  above,  but  use  only  about  one-third 
the  amount  of  nitric  and  hydrochloric  acids  for  the  solution.  Before 
adding  the  molybdate  solution,  the  volume  of  the  filtrate  from  the  silica 
should  amount  to  only  about  25  c.c.  Add  50  c.c.  of  the  molybdate  solu- 
tion, allow  it  to  stand  four  hours  at  a  temperature  of  40°  C.,  and  filter  off 
the  precipitated  phospho-molybdate  on  a  Gooch  crucible ;  wash  first  with 

*  Jour,  fur  Pr.  Chem.,  Ixxix.  496. 


DETERMINATION  OF  PHOSPHORUS.  9! 

dilute  molybdate  solution,  and  finally  with  water  containing  I  per  cent,  of 
nitric  acid,  dry  in  an  air-bath  heated  to  120°  C.,  and  weigh  as  ammonium 
phospho-molybdate,  containing  1.63  per  cent,  of  phosphorus.  In  the 
absence  of  a  Gooch  crucible,  use  counterpoised  filters  *  for  weighing  the 
phospho-molybdate.  The  points  of  special  importance  are : 

First,  the  necessity  for  destroying  all  the  carbonaceous  matter  by  heat- 
ing the  nitric  acid  solution,  after  evaporation,  to  a  sufficiently  high  temper- 
ature to  effect  this  with  certainty. 

Second,  the  avoidance  of  the  presence  of  hydrochloric  acid  in  the  final 
solution  before  precipitating  by  molybdate  solution. 

Third,  when  the  phospho-molybdate  is  weighed  directly,  the  necessity 
for  rendering  the  silica  insoluble. 

Fourth,  the  danger  of  heating  the  solution  above  40°  C.  after  adding 
the  molybdate  solution,  as  arsenic,  when  present,  precipitates  with  the 
phosphorus  if  the  solution  is  heated  to  a  higher  temperature. 

Fifth,  the  danger  of  causing  a  precipitation  of  molybdic  acid  with  the 
phospho-molybdate  by  heating  the  solution  to  a  temperature  approximating 

100°  C. 

The  Combination  Method. 

Rileyf  was  the  first  to  suggest  the  precipitation  of  phosphorus  as 
phospho-molybdate,  preceded  by  a  separation  of  the  phosphoric  acid  from 
the  mass  of  the  ferric  chloride  by  deoxidation  and  precipitation  by  the 
acetate  method.  This  method  was  worked  out  afterwards  by  A.  Wendel, 
of  the  Albany  and  Rensselaer  Steel  Company,  S.  Peters,  of  the  Burden 
Iron  Company,  and  J.  L.  Smith.  \ 

Proceed  as  directed  for  the  determination  of  phosphorus  by  the  Acetate 
Method,  using  I  gramme  of  borings  and  proportional  amounts  of  reagents 
until  having  dissolved  the  acetate  precipitate  in  hydrochloric  acid,  evaporate 
to  dryness,  redissolve  in  a  very  little  nitric  acid,  dilute  to  20  c.c.  with  water, 
add  a  slight  excess  of  ammonia,  redissolve  the  precipitated  ferric  oxide  in 
nitric  acid,  and  add  30  c.c.  molybdate  solution.  *  Heat  to  40°  C.  for  an  hour, 
filter,  wash  with  water  containing  I  per  cent,  of  nitric  acid,  dry,  and  weigh. 

*  See  page  28.  |  Jour.  Chem.  Soc.,  1878,  i.  104. 

|  Chem.  News,  xlv.  195. 


92  ANAL  YSIS   OF  IRON  AND   STEEL. 

When  Titanium  is  Present. 

When  determining  phosphorus  in  pig-irons  containing  titanium,  burn 
off  the  residue  of  carbon,  silica,  etc.,  treat  it  with  hydrofluoric  and  sul- 
phuric acids,  evaporate,  and  heat  until  the  greater  part  of  the  sulphuric 
acid  is  driven  off.  Fuse  with  2  or  3  grammes  of  sodium  carbonate,  dis- 
solve in  water,  filter,  acidulate  the  filtrate  with  nitric  acid,  add  50  c.c. 
molybdate  solution,  and  heat  to  40°  C.  for  four  hours.  Filter,  wash,  and 
add  this  precipitate  to  the  one  obtained  in  the  filtrate  from  the  carbon, 
silica,  etc.  If  any  slight  insoluble  matter  should  remain  on  the  filter 
upon  dissolving  in  ammonia  the  phospho-molybdate  obtained  in  the 
filtrate  from  the  carbon,  silica,  etc.,  burn  it,  fuse  it  with  sodium  carbonate, 
and  test  it  also  for  phosphorus. 

The  composition  of  the  dried  ammonium  phospho-molybdate  seems  to 
vary  very  much,  the  percentage  of  phosphorus  in  it  being  given  by  various 
authorities  from  1.27  to  1.75.  It  seems  to  depend  upon  various  circum- 
stances, such  as  the  presence  or  absence  of  hydrochloric  acid  in  the 
solution,  the  degree  of  acidity,  the  temperature  at  which  the  precipitation 
is  effected,  the  length  of  time  the  solution  stands  before  the  precipitate  is 
filtered  off,  the  size  of  the  precipitate,  the  state  of  concentration  of  the 
solution,  and  even  the  amounts  of  the  iron  and  ammonium  salts  present. 

This  fact  must  be  borne  in  mind  when  the  phosphorus  is  determined  by 
direct  weighing  of  the  phospho-molybdate,  and  every  effort  must  be  used 
to  effect  the  precipitations  always  under  as  nearly  as  possible  the  same 
conditions. 

RAPID    METHODS. 

Volumetric  Method.* 
Reduction  by  Zinc  arid  Titration  by  Permanganate  Solution. 

This  method  gives  an  indirect  determination  of  phosphorus  by  means  of 
the  estimation  of  the  molybdic  acid  in  the  ammonium  phospho-molybdate, 

*  This  method  is  the  one  prepared  by  the  sub-committee  on  Methods  of  the  International  Steel 
Standards  Committee  of  the  United  States.  It  is  by  far  the  best  method  known,  and  the  results 
obtained  by  it  are  exceedingly  accurate  when  the  details  are  carefully  observed.  The  sub-committee 
consists  of  W.  P.  Barba,  A.  A.  Blair,  T.  M.  Drown,  C.  B.  Dudley  (chairman),  and  P.  W.  Shimer. 


RAPID   METHODS  FOR   PHOSPHORUS. 


93 


FIG.  51. 


in  which  form  the  phosphorus  is  precipitated.    The  molybdic  acid  is  reduced 
to  a  lower  state  of  oxidation  by  the  reducing  action  of  zinc  and  sulphuric  acid, 
and  the  reduced  oxide  is  titrated 
with  a  standardized  permanga- 
nate solution,  molybdic  acid  be- 
ing again  formed  by  the  reaction. 

Fig.  5 1  shows  a  form  of 
shaking-machine  for  shaking 
four  flasks  at  once.  The  con- 
struction and  method  of  use 
are  apparent  from  the  sketch. 

Fig.  52  shows  a  form  of 
reductor  which  is  most  con- 
venient and  efficient.  The  tube 
a  is  0.018  m.  inside  diameter 
and  0.300  m.  long.  The  small 
tube  below  the  contraction  with 
the  stopcock  c  is  0.006  m.  in 
inside  diameter  and  0.300  m. 
long  below  the  stopcock.  The 

tube  is  filled  by  placing  at  the  point  of  contraction  a  flat  piece  of 
fine  platinum  gauze.  On  top  of  this  is  placed  a  plug  of  glass  wool, 
about  8  mm.  thick,  and  then  asbestos,  previously  treated  with  concen- 
trated hydrochloric  acid,  thoroughly  washed,  ignited,  and  diffused  in 
water,  is  poured  into  the  reductor  tube  until  it  forms  a  coating  on  top 
of  the  glass  wool  not  over  I  mm.  thick.  This  makes  a  filter  which  pre- 
vents very  small  pieces  of  zinc  or  other  materials  from  being  carried 
through.  It  is  necessary  to  clean  and  refill  the  tube  from  time  to  time, 
as  the  filter  after  some  use  becomes  clogged  and  the  liquid  passes  too 
slowly.  The  tube  is  filled,  as  shown  in  the  cut,  with  granulated  amal- 
gamated zinc.  The  reductor  tube  is  fixed  at  such  a  height  that  when  the 
block  is  removed  from  under  the  flask  /,  the  latter  may  readily  be  de- 
tached from  the  tube  and  removed  without  disturbing  the  apparatus. 

Fig.  53  shows  the  burette  arranged  for  running  the  potassium  perman- 


94 


ANAL  YSIS   OF  IRON  AND   STEEL. 


ganate  directly  into  the  flask,  and    needs    no  explanation.     It  should  be 
carefully  calibrated. 

FIG.  52.  FIG.  53. 


The  various  beakers,  flasks,  graduates,  etc.,  required  by  this  method 
need  no  special  comment. 

Reagents. 

Nitric  Acid. — Nitric  acid  of  1.135  sp.  gr.,  made  by  mixing  C.  P.  nitric 
acid  (1.42  sp.  gr.)  with  about  three  parts  of  distilled  water. 

Strong  Sulphuric  Acid. — The  C.  P.  material  of  1.84  sp.  gr. 

Dilute  Sulphuric  Acid. — Sulphuric  acid  2^/2  per  cent.,  by  volume,  made  by 
diluting  25  c.c.  of  concentrated  C.  P.  sulphuric  acid  to  I  litre  with  distilled 
water. 

Strong  Ammonia. — The  C.  P.  material  of  0.90  sp.  gr. 


RAPID   METHODS  FOR   PHOSPHORUS.  95 

Dilute  Ammonia  (0.96  sp.  gr.). — Made  by  mixing  concentrated  C.  P. 
ammonia-water  of  0.90  sp.  gr.  with  about  one  and  a  half  times  its  volume 
of  distilled  water. 

Strong  Solution  of  Potassium  Permanganate,  for  oxidizing  the  phos- 
phorus and  carbonaceous  matter  in  the  nitric  acid  solution  of  a  steel. 
Made  by  dissolving  from  12.5  to  15  grammes  of  crystallized  potassium  per- 
manganate in  I  litre  of  distilled  water  and  filtering  through  asbestos. 

Standard  Solution  of  Potassium  Permanganate,  for  titrating  the  reduced 
solutions  of  ammonium  phospho-molybdate.  Made  by  dissolving  2 
grammes  of  crystallized  potassium  permanganate  in  I  litre  of  distilled 
water  and  filtering  through  asbestos.  This  solution  is  standardized  as 
follows.  Place  from  0.15  to  0.25  gramme  of  thoroughly  cleaned  soft  steel 
wire,  in  which  the  iron  has  been  carefully  determined,  in  each  of  three 
125  c.c.  Erlenmeyer  flasks,  and  pour  into  each  of  the  flasks  30  c.c.  of 
distilled  water  and  10  c.c.  of  strong  sulphuric  acid.  Cover  with  a  small 
watch-glass  and  heat  until  solution  is  complete.  Add  a  sufficient  amount 
of  the  strong  solution  of  potassium  permanganate  to  oxidize  the  iron  and 
destroy  the  carbonaceous  matter,  being  careful  to  avoid  an  excess  which 
would  cause  a  precipitate  of  manganese  dioxide.  Should  this  occur, 
redissolve  it  by  adding  a  very  few  drops  of  sulphurous  acid  and  boil  off 
every  trace  of  the  latter.  Allow  the  solution  in  the  flasks  to  cool  and  add 
to  each  10  c.c.  of  dilute  ammonia.  Pass  through  the  reductor  and  titrate 
in  the  flask. 

In  all  cases  the  mode  of  procedure  in  using  the  reductor  should  be  as 
follows.  Everything  being  clean  and  in  good  order  from  previous  treat- 
ment with  dilute  sulphuric  acid,  and  washing  with  distilled  water,  and  the 
flask  being  attached  to  the  filter  pump,  pour  100  c.c.  of  warm  dilute 
sulphuric  acid  into  the  funnel  and  open  the  stopcock  c.  When  only  a  little 
remains  in  the  funnel  forming  the  top  of  the  reduction  tube,  transfer  the 
solution  to  be  reduced  to  the  funnel.  This  solution  should  be  hot  but  not 
boiling.  Pour  some  of  the  dilute  sulphuric  acid  into  the  vessel  which 
contained  the  solution  to  be  reduced  to  wash  it,  and  when  only  a  little 
solution  is  left  in  the  funnel  as  before,  add  this  to  the  funnel  in  such  a  way 
as  to  wash  it  and  follow  with  about  200  c.c.  more  of  warm  dilute  sulphuric 


g6  ANAL  YSIS  OF  IRON  AND   STEEL. 

acid  and  finally  with  50  c.c.  of  hot  distilled  water.  In  no  case  allow  the 
funnel  to  get  empty,  and  close  the  stopcock  c  when  there  is  still  a  little 
of  the  wash-water  left  in  the  funnel  above  the  surface  of  the  zinc.  This 
precaution  prevents  air  from  passing  into  the  reductor  tube.  A  blank 
determination  is  made  by  passing  through  the  reductor  a  solution  contain- 
ing a  mixture  of  10  c.c.  strong  sulphuric  acid,  10  c.c.  dilute  ammonia, 
and  50  c.c.  water ;  preceded  and  followed  by  the  dilute  acid  as  described 
above.  The  amount  of  potassium  permanganate  required  to  give  this  blank 
a  distinct  color  is  subtracted  from  the  amount  required  to  give  the  same 
color  to  each  reduced  solution. 

To  get  the  value  of  the  permanganate  solution,  multiply  the  weight  of 
iron  wire  taken  by  the  percentage  of  iron  in  the  wire  and  divide  by  the 
number  of  cubic  centimetres  of  potassium  permanganate  in  terms  of 
metallic  iron.  Multiply  this  result  by  0.88163,  the  ratio  of  molybdic 
acid  to  iron,  and  the  product  by  0.01794,  the  ratio  of  phosphorus  to 
molybdic  acid,  and  the  result  is  the  value  of  I  c.c.  of  the  permanganate 
solution  in  terms  of  phosphorus.  The  ratio  of  molybdic  acid  to  iron  given 
above  is  that  found  when  a  known  amount  of  molybdic  acid  in  sulphuric 
acid  solution  is  passed  through  the  reductor  in  the  manner  described  above 
and  then  titrated  with  potassium  permanganate  solution  whose  strength 
in  terms  of  metallic  iron  is  known.  The  reduction  of  the  molybdic  acid 
in  the  reductor  in  this  case  is  to  the  form  Mo24O37.  The  ratio  of  phos- 
phorus to  molybdic  acid  given  above  is  that  found  by  the  analysis  of  the 
yellow  precipitate  of  ammonium  phospho-molybdate  obtained  from  nitric 
acid  solution  of  iron  under  varying  conditions. 

Sulphurous  Acid. — A  strong  solution  of  the  gas  in  water.  Siphons  of 
the  liquefied  gas  may  be  obtained  in  the  market. 

Acid  Ammonium  Sulphite. — The  strong  C.  P.  solution  of  the  reagent 
diluted  with  10  parts  of  water. 

Ferrous  Sulphate. — Crystals  of  the  salt  free  from  phosphorus. 

Sodium   Thiosulphate. — Crystals  of  the  salt  free  from  phosphorus. 

These  four  reagents  are  for  reducing  the  excess  of  binoxide  of  man- 
ganese thrown  down  in  oxidizing  the  carbonaceous  matter  in  the  nitric 
acid  solutions  of  the  steels.  Any  one  may  be  used. 


RAPID   METHODS  FOR   PHOSPHORUS.  97 

Molybdate  Solution.— Place  in  a  beaker  100  grammes  of  pure  molybdic 
anhydride,  mix  it  thoroughly  with  400  c.c.  cold  distilled  water  and  add 
80  c.c.  strong  ammonia  (0.90  sp.  gr.).  When  solution  is  complete,  filter 
and  pour  the  filtered  solution  slowly  and  with  constant  stirring  into  a 
mixture  of  400  c.c.  strong  nitric  acid  (1.42  sp.  gr.)  and  600  c.c.  distilled 
water.  Add  50  milligrammes  of  microcosmic  salt  dissolved  in  a  little 
water,  agitate  thoroughly,  allow  the  precipitate  to  settle  for  twenty-four 
hours,  and  filter  before  using. 

Acid  Ammonium  Sulphate  Solution,  for  washing  the  precipitate  of 
ammonium  phospho-molybdate.  To  I  litre  of  water  add  15  c.c.  of 
strong  ammonia  (0.90  sp.  gr.)  and  25  c.c.  strong  sulphuric  acid  (1.84 
sp.  gr.). 

Amalgamated  Zinc. — Dissolve  5  grammes  of  mercury  in  25  c.c. 
strong  nitric  acid  diluted  with  an  equal  bulk  of  water,  dilute  to  250  c.c. 
and  transfer  to  a  stout  flask  of  about  1000  c.c.  capacity.  Pour  into  it 
500  grammes  of  granulated  zinc  which  will  pass  through  a  2O-mesh 
sieve,  but  not  through  a  3O-mesh.  Shake  it  thoroughly  for  a  minute 
or  two  and  then  pour  off  the  solution,  wash  the  zinc  thoroughly  with 
distilled  water,  dry,  and  preserve  in  a  glass  bottle  for  use. 

Operation. 

Weigh  2  grammes,  or,  in  case  of  steels  containing  over  0.15  per  cent, 
phosphorus,  I  gramme  of  the  drillings  and  transfer  them  to  a  250  c.c. 
Erlenmeyer  flask,  pour  into  the  flask  100  c.c.  of  nitric  acid  (1.135  sp.  gr.) 
and  cover  with  a  small  watch-glass.  Heat  until  the  solution  is  complete 
and  nitric  oxide  is  boiled  off.  Add  10  c.c.  of  the  strong  potassium 
permanganate  solution,  boil  until  the  pink  color  has  disappeared  and 
manganese  dioxide  separates.  Continue  the  boiling  for  several  minutes, 
then  remove  from  the  source  of  heat  and  add  a  few  drops  of  sulphurous 
acid,  a  small  crystal  of  ferrous  sulphate,  or  a  solution  of  0.5  gramme  of 
sodium  hyposulphite  in  10  c.c.  of  water,  repeating  the  addition  at  short 
intervals  until  the  precipitated  manganese  dioxide  is  dissolved.  Boil 
two  minutes  longer,  place  the  flask  in  a  vessel  of  cold  water,  or  allow 
it  to  stand  in  the  air  until  it  feels  cool  to  the  hand,  and  then  pour  in 

7 


98  ANAL  YSIS   OF  IRON  AND   STEEL. 

40  c.c.  of  dilute  ammonia  (0.96  sp.  gr.).  The  precipitated  ferric  hydrate 
will  redissolve  when  the  liquid  is  thoroughly  mixed.  When  the  solution 
is  about  the  temperature  of  the  hand,  say  35°  C,  add  40  c.c.  of  molybdate 
solution  at  the  ordinary  temperature,  close  the  flask  with  a  rubber  stopper, 
and  shake  it  for  five  minutes,  either  by  hand  or  in  the  machine,  Fig.  51. 
Allow  the  precipitate  to  settle  for  a  few  minutes,  filter  on  a  0.090  m.  filter, 
and  wash  with  acid  ammonium  sulphate  solution  until  2  or  3  c.c.  of  the 
wash-water  give  no  reaction  for  molybdenum  with  a  drop  of  ammonium 
sulphide.  Pour  5  c.c.  of  ammonia  (0.90  sp.  gr.)  and  20  c.c.  of  water 
into  the  flask  to  dissolve  any  adhering  ammonium  phospho-molybdate 
and  then  pour  it  on  the  precipitate  in  the  filter,  allowing  the  filtrate 
to  run  into  a  250  c.c.  Griffin's  beaker.  Wash  out  the  flask  and  wash 
the  filter  with  water  until  the  solution  measures  about  60  c.c.  Add 
to  the  liquid  in  the  beaker  10  c.c.  strong  sulphuric  acid,  and  pass  it 
through  the  reductor  exactly  in  the  manner  described  for  the  solution 
of  ferric  sulphate  in  standardizing  the  solution  of  potassium  permanganate, 
being  careful  to  keep  the  end  of  the  small  tube  of  the  reductor  just 
below  the  surface  of  the  liquid  in  the  flask.  By  adding  the  strong 
sulphuric  acid  to  the  ammoniacal  solution  immediately  before  passing 
it  through  the  reductor  it  is  heated  sufficiently  by  the  chemical  action 
to  insure  thorough  reduction.  In  washing  be  careful  that  no  air  passes 
into  the  reductor,  and  when  the  water  has  been  drawn  through,  leaving 
a  little  still  remaining  in  the  funnel,  close  the  stopcock,  detach  the  flask 
F,  wash  off  the  drawn-out  portion  of  the  reductor  tube  into  it,  and 
titrate  the  solution  with  the  standard  permanganate.  The  reductor 
should  be  so  arranged  that  the  whole  reduction  occupies  about  three  or 
four  minutes.  The  solution  that  passes  through  should  be  bright  green 
in  color.  In  adding  the  permanganate,  the  green  color  disappears  first, 
and  the  solution  becomes  brown,  then  pinkish  yellow,  and  ultimately 
colorless.  Continue  the  addition  of  the  permanganate  drop  by  drop, 
shaking  the  flask  vigorously  until  the  solution  assumes  a  faint  pink 
coloration,  which  remains  after  standing  one  minute.  Subtract  from 
the  reading  of  the  burette  the  amount  given  by  a  blank  determination, 
obtained  exactly  as  described  under  the  method  given  above  for  standard- 


RAPID   METHODS  FOR   PHOSPHORUS.  99 

izing  the  permanganate  solution,  multiply  the  number  of  c.c.  so  obtained 
by  the  value  of  I  c.c.  in  terms  of  phosphorus,  multiply  by  100  and  divide 
by  the  weight  taken,  and  the  result  is  the  percentage  of  phosphorus  in 
the  steel. 

When  a  large  number  of  analyses  are  to  be  carried  along  at  once 
the  following  modification  is  recommended.  Obtain  the  yellow  pre- 
cipitate and  dissolve  in  ammonia  exactly  as  described  above,  except 
that  the  solution  is  allowed  to  run  into  the  flask  in  which  the  pre- 
cipitation was  made,  and  the  washing  of  the  filter  is  continued  until 
the  solution  amounts  to  75  c.c.  Add  now  to  the  flask  5  grammes  of 
pulverized  zinc,  loo-mesh,  pouring  it  into  the  flask  through  a  funnel 
to  prevent  any  zinc  clinging  to  the  sides  of  the  flask.  Then  add  to 
the  flask  15  c.c.  strong  sulphuric  acid  (1.84  sp.  gr.).  This  is  most  con- 
veniently done  in  practice  by  letting  it  run  in  from  a  glass-stoppered 
burette.  Close  the  flask  at  once  with  a  rubber  stopper  carrying  a 
glass  tube  bent  twice  at  right  angles,  the  farther  arm  dipping  into  a 
beaker  containing  a  saturated  solution  of  sodium  bicarbonate.  The 
flask  should  now  stand  undisturbed  for  about  thirty  minutes,  when,  if 
all  action  has  ceased,  it  is  ready  to  titrate  with  permanganate.  The 
solution  should  be  green,  not  brown.  The  temperature  of  the  solution 
at'  the  end  of  thirty  minutes  is  about  40°  C.  and  the  titration  succeeds 
best  if  done  at  this  temperature.  But  the  flask  may  stand  a  couple 
of  hours  without  reoxidation  of  the  reduced  molybdic  acid,  and  may 
then  be  successfully  titrated.  If  .  the  solution  changes  in  color  to 
brown  the  determination  should  be  rejected,  as  the  result  will  be 
too  low.  A  blank  should  be  made  by  adding  to  another  flask  65 
c.c.  of  water,  10  c.c.  of  dilute  ammonia  (0.96  sp.  gr.),  5  grammes  of 
the  loo-mesh  zinc,  added  in  the  manner  described,  and  15  c.c.  of 
strong  sulphuric  acid  (1.84  sp.  gr.).  This  flask  should  be  treated  the 
same  as  the  others  and  the  amount  of  permanganate  it  uses  up 
should  be  deducted  from  the  amount  required  by  each  flask  con- 
taining a  test.  When  this  method  is  used  the  reduction  is  prac- 
tically complete  to  molybdic  acid,  so  that  the  factor  0.85714  must 
be  used  instead  of  0.88163. 


IOO  ANAL  YSIS   OF  IRON  AND   STEEL. 

Example. 

0.1745  gramme  of  wire  requires  50  c.c.  of  permanganate  to  give  the 
required  color.  A  blank  determination  gave  O.I  c.c.,  so  that  the  wire 
actually  required  49.9  c.c.  permanganate.  The  wire  contained  99.87  per 
cent,  of  iron,  then  0.1745  X  0.9987  -s-  49.9  equals  0.0034923,  or  r  c.c.  of 
permanganate  equals  0.0034923  gramme  metallic  iron.  Then  multiplying 
the  value  in  iron  by  the  ratio  of  molybdic  acid  to  iron  0.88163  or  085714 
and  the  product  by  the  ratio  of  phosphorus  to  molybdic  acid  0.01794,  we 
have  0.0034923  X  0.88163  X  001794  equals  0.000055238,  or  I  c.c.  perman- 
ganate equals  0.000055238;  gramme  of  phosphorus.  Again,  the  precipi- 
tated ammonium  phospho-rnolybdate  from  2  grammes  of  steel  required  35.6 
c.c.  permanganate  less  blank  o.i  c.c.  equals  35.5  c.c.;  35.5  X  0.000055238 
X  IOO  -i-  2  equals  0.098  per  cent,  phosphorus. 

Notes  and  Precautions. 

It  will  be  observed  that  the  method  given  above  oxidizes  the  phos- 
phorus in  the  iron  by  means  of  nitric  acid,  completes  and  perfects  this 
oxidation  and  possibly  neutralizes  the  effect  of  the  carbon  present  by 
means  of  potassium  permanganate,  and  then  separates  the  phosphoric 
acid  from  the  iron  by  means  of  molybdic  acid.  The  molybdic  acid  in 
the  yellow  phosphomolybdate  is  subsequently  determined  by  means  of 
potassium  permanganate,  the  phosphorus  being  determined  from  its  rela- 
tion to  the  molybdic  acid  in  this  precipitate.  The  method  given  above 
applies  to  steel  and  wrought  iron,  but  it  is  not  yet  recommended  for 
pig-iron. 

It  is  hardly  necessary  to  say  that  all  the  chemicals  and  materials  used 
in  the  analysis  are  assumed  to  be  free  from  impurities  that  will  injuriously 
affect  the  result. 

1.135  sp.  gr.  nitric  acid  apparently  oxidizes  the  phosphorus  just  as 
successfully  as  a  stronger  one,  while  by  its  use  solution  is  sufficiently 
rapid,  and  there  is  less  trouble  during  the  subsequent  filtration  due  to 
silica. 

The  boiling  of  the  solution  to  remove  nitrous  acid  and  assist  the  action 


RAPID   METHODS  FOR   PHOSPHORUS.  IOI 

of  the  oxidizing  permanganate  seems  to  be  essential.  Some  steels  may  not 
require  10  c.c.  of  the  permanganate  and  some,  like  washed  metal  high  in 
carbon,  may  require  even  more.  It  is  essential  that  enough  should  be 
added  to  cause  a  precipitation  of  manganese  dioxide  and  to  give  a  strong 
pink  color  to  the  solution.  This  color  gradually  disappears  on  boiling. 
Less  is  required  if  the  permanganate  is  added  in  small  successive  portions. 
Boiling  two  minutes  after  reducing  the  manganese  dioxide  removes  any 
nitrous  acid  that  may  be  formed  by  that  operation. 

In  washing  the  yellow  precipitate  it  shows  some  disposition  to  crawl  up 
to  the  top  of  the  filter.  Care  should  therefore  be  taken  to  have  the  filter 
fit  the  funnel  so  closely  that  even  if  the  precipitate  does  crawl  over  the  top 
it  will  not  be  lost  while  washing  the  filter  completely  to  the  top.  It  is 
very  easy  to  leave  enough  molybdic  acid  in  the  top  of  the  filter,  even 
though  the  washings  are  tested,  to  cause  an  error  of  .005  per  cent,  in  the 
determination. 

It  is  best  to  make  up  molybdate  solution  rather  frequently.  It  is  also 
best  to  keep  it  in  the  dark  at  a  temperature  not  above  28°  or  30°  C.  Much 
of  the  so-called  molybdic  acid  of  the  market  is  ammonium  molybdate  or 
molybdate  of  some  other  alkali.  This  fact  cannot  be  ignored  in  making 
up  the  molybdate  solution.  A  series  of  experiments  with  various  molyb- 
dic acids  and  alkaline  molybdates  obtained  in  the  market  indicates  that  if 
the  amount  of  molybdic  acid  in  the  solution  is  that  called  for  by  the 
formula,  irrespective  of  whether  this  amount  is  furnished  by  pure  molybdic 
acid  or  by  any  of  the  commercial  molybdates  referred  to,  the  result  will  be 
much  nearer  the  truth  than  if  this  is  not  done.  Good  molybdic  acid  is  the 
best,  but  the  alkaline  molybdates  can  be  used.  The  amount  of  molybdic 
acid  in  these  molybdates  can  readily  be  determined  by  dissolving  o.iooo 
gramme  in  60  c.c.  of  water  to  which  10  c.c.  of  dilute  ammonia  have  been 

o 

added,  filtering,  adding  10  c  c.  strong  C.  P.  sulphuric  acid,  and  passing 
through  the  reductor  as  above  described.  The  method  given  in  the 
example  above  enables  the  amount  of  molybdic  acid  to  be  determined. 
If  the  molybdic  acid  as  obtained  in  the  market,  or  the  ammonia  used  in 
dissolving  it,  contains  any  soluble  silicates,  the  resulting  molybdate  solution 
will  be  yellowish  in  color  and  the  determination  made  with  this  solution 


102  ANALYSIS    OF  IRON  AND   STEEL. 

will  be  high,  owing  apparently  to  ammonium  silico-molybdate  being  dragged 
do»vn  with  the  phospho-molybdate.  Treatment  of  the  molybdate  solution 
with  microcosmic  salt,  as  described,  overcomes  this  difficulty  and  gives  a 
perfectly  colorless  molybdate  solution.  A  molybdate  solution  tinged  with 
yellow  should  never  be  used.  It  will  be  observed  that  the  molybdate 
solution  recommended  above  contains  much  less  ammonium  nitrate  than  is 
given  by  many  of  the  formulas  now  in  use.  Experience  shows  that  a 
molybdate  solution  made  on  this  formula  keeps  much  better  than  those 
containing  more  ammonium  nitrate.  It  will  also  be  observed  that  the 
amount  used  for  each  determination  is  less  than  many  methods  employ. 
It  is  believed  that  the  amount  recommended  is  sufficient  and  that  the 
ammonium  nitrate 'required  to  assist  the  formation  of  the  yellow  precipitate 
is  furnished  by  the  40  c.c.  of  dilute  ammonia  added  to  the  nitric  acid 
solution  of  the  steel.  Of  course  the  molybdate  solution  recommended 
above  cannot  be  used  for  other  work  interchangeably  with  that  made  on 
the  older  formulas,  on  account  of  lack  of  ammonium  nitrate. 

The  directions  in  regard  to  the  reductor,  both  as  to  making  and  use, 
should  be  strictly  followed.  By  the  use  of  the  stopcock  and  the  amal- 
gamated zinc,  and  by  keeping  a  little  liquid  in  the  funnel,  the  same  blank 
can  be  obtained  from  a  reductor  almost  continuously,  even  though  two  or 
three  days  of  standing  intervene  between  blanks.  It  is,  however,  always 
advisable  to  treat  with  dilute  sulphuric  acid  and  wash  before  using,  even 
though  only  one  night  has  elapsed  since  the  last  previous  use.  If  the 
solution  to  be  reduced  does  not  contain  enough  acid  or  is  not  warm 
enough,  the  reduction  will  not  be  complete.  Care  should  therefore  be 
taken  not  to  allow  too  much  mixing  of  the  dilute  sulphuric  acid  with  the 
solution  to  be  reduced,  either  in  the  funnel  or  in  the  reductor  tube  itself. 
The  best  asbestos  to  use  is  the  mineral  known  as  actinolite,  but  any  fibrous 
mineral  which  will  act  as  a  filter  and  not  be  dissolved  by  the  acids  used 
may  be  employed.  Glass  wool  alone  will  not  do,  as  a  good  filter  is 
essential  in  order  that  neither  small  particles  of  zinc  nor  impurities  in  the 
zinc  may  be  drawn  down  into  the  flask  with  the  reduced  solution.  The 
consumption  of  zinc  is  very  small. 

In  testing  with  ammonium  sulphide,  to  see  whether  the  washing  of  the 


RAPTD   METHODS  FOR   PHOSPHORUS.  103 

yellow  precipitate  is  complete,  good  results  are  obtained  by  putting  two 
or  three  drops  of  yellow  ammonium  sulphide  into  a  few  cubic  centimetres 
of  distilled  water,  and  allowing  the  washings  to  drop  into  this  solution 
from  the  stem  of  the  funnel.  If  iron  is  present  in  the  washings  it  will 
show  while  the  solution  is  still  alkaline.  By  allowing  the  washings  to 
continue  running  into  the  ammonium  sulphide  solution  it  soon  becomes 
acid,  when  molybdenum,  if  any  is  present,  shows  by  a  more  or  less  brown- 
ish color.  If  the  acid  solution  is  pure  white  from  separated  sulphur  the 
washing  is  complete. 

Since  the  acidity  of  the  solution  in  which  the  yellow  precipitate  is 
formed  has  an  influence  on  its  composition,  it  is  quite  desirable  that  the 
sp.  gr.  of  the  1.135  nitric  acid  and  of  the  0.96  ammonia  should  be  taken 
with  some  care.  The  temperature  at  which  the  figures  are  correct  is  15° 
C.  It  is  best  to  use  the  Westphal  balance  in  determining  these  gravities, 
but,  failing  this,  a  sufficiently  delicate  hydrometer  may  be  employed. 

In  using  the  reduction  with  5  grammes  of  loo-mesh  zinc,  it  will  be 
observed  that  as  the  zinc  becomes  nearly  all  dissolved  a  blackish  residue 
remains.  This  residue  seems  to  be  metallic  lead.  It  disappears  slowly 
during  the  titration  and  apparently  uses  up  some  permanganate.  It  takes  a 
little  longer  to  secure  a  satisfactory  end  reaction  with  the  loo-mesh  zinc, 
as  the  pink  color  fades  out  several  times  before  it  will  remain  permanent  for 
one  minute.  It  is  essential  that  air  should  be  excluded  from  the  flask  after 
the  reduction  is  nearly  complete,  and  it  is  for  this  purpose  that  the  sodium 
bicarbonate  solution  is  used.  A  tendency  to  suck  the  soda  solution  back 
into  the  reducing  flask  will  be  noticed,  due  to  the  cooling  of  the  flask. 
The  reduction  should  be  made  in  a  place  free  from  draughts. 

With  the  amalgamated  zinc  in  the  reductor  made  as  above  described 
the  blank  generally  uses  up  about  o.i  c.c.  of  the  standard  permanganate 
solution.  The  blank  when  using  the  reduction  by  means  of  5  grammes 
loo-mesh  zinc  usually  amounts  to  0.6  c.c.  of  the  standard  permanganate, 
and  may  be  higher.  Pulverized  zinc  is  rarely  free  from  sulphides,  and 
while  this  seems  not  to  be  a  very  important  matter,  it  is  nevertheless  not 
recommended  to  use,  either  in  the  reductor  or  in  the  flask  reduction,  a  zinc 
that  gives  a  high  blank. 


104  ANALYSIS   OF  IRON  AND   STEEL. 

If  the  amount  of  sulphurous  acid  or  other  reagent  added  to  the  nitric 
acid  solution  to  remove  the  precipitated  binoxide  of  manganese  is  insuffi- 
cient, a  brown  stain  will  be  left  on  the  filter-paper  after  the  yellow  precipi- 
tate is  dissolved  in  ammonia.  This  may  occur  even  though  the  nitric  acid 
solution  looks  clear,  and  as  no  harm  can  arise  from  a  slight  excess  of  the 
reducing  agent,  it  is  usually  more  satisfactory  to  add  an  excess.  It  is  not 
desirable  to  add  the  reducing  agent  to  the  solution  while  boiling,  as  under 
such  circumstances  it  frequently  boils  over. 

It  is  rather  essential  to  use  the  dilute  sulphuric  acid  warm,  so  that  the 
general  temperature  of  the  reductor  may  be  kept  up. 

A  good  method  for  cleaning  the  wire  in  standardizing  the*  potassium 
permanganate  is  as  follows.  Take  a  round  lead-pencil  and  make  a  hole 
in  it  with  a  pin  near  the  end.  Insert  the  end  of  the  wire  in  this  hole  and 
revolve  the  pencil  until  there  are  two  turns  of  the  wire  around  it.  Hold 
the  turns  firmly  in  one  hand  and  cut  the  wire  so  that  about  0.75  m.  will 
remain  attached  to  the  pencil.  Draw  this  wire  through  a  piece  of  folded 
fine  sand-paper  several  times  and  then  several  times  through  a  piece  of 
filter-paper.  Seize  the  wire  near  the  pencil  with  the  filter-paper  and  cut  off 
the  part  which  was  wound  around  the  pencil  and  remove  it.  Then  insert 
the  end  of  the  cleaned  wire  in  the  hole  and  revolve  the  pencil  with  one 
hand,  holding  the  wire  in  the  filter-paper  in  the  other  hand,  until  it  is  all 
wound  loosely  on  the  pencil.  Push  the  coiled  wire  off  the  end  of  the 
pencil.  It  is  now  in  a  convenient  form  for  weighing. 

Alkalimetric  Method.* 

The  principle  on  which  this  method  is  based  is  the  acidity  of  ammonium 
phospho-molybdate,  which,  according  to  the  following  reaction,  requires  23 
molecules  of  alkali  for  its  neutralization. 

2[(NH4)3i2Mo03P04]  +  46NaHO  +  H,O  =  2  [(NH4),HPOJ  +  (NH4)2 
MoO4  -f  23Na2MoO4 


*  This  method  was  first  suggested  by  Mr.  C.  E.  Manby  and  subsequently  modified  by  Mr. 
James  O.  Handy,  of  Pittsburg,  to  whose  work  many  of  the  details  are  due.  It  is  quite  extensively 
used  and  is  extremely  rapid.  Mr.  Handy  kindly  prepared  the  essential  part  of  this  description. 


RAPID   METHODS  FOR   PHOSPHORUS.  1 05 

Reagents. 

Molybdate  Solution. — The  solution  described  in  the  last  method  (page 
97)  may  be  used. 

Nitric  Acid  for  Washing  Precipitates. — A  I  per  cent,  solution  of  nitric 
acid:  add  13  c.c.  of  strong  nitric  acid  (1.42  sp.  gr.)  to  I  litre  of  water. 

Potassium  Nitrate  Solution. — A  i  per  cent,  solution  of  potassium  nitrate: 
dissolve  I  gramme  of  potassium  nitrate  in  I  litre  of  water. 

Phenolphthalein  Solution. — A  0.2  per  cent,  solution  of  phenolphthalein : 
dissolve  I  gramme  of  phenolphthalein  in  500  c.c.  of  95  per  cent,  alcohol. 

Standard  Solution  of  Sodium  Hydroxide. — To  100  grammes  pure 
sodium  hydroxide  add  an  amount  of  water  just  insufficient  to  com- 
pletely dissolve  it.  Pour  it  into  a  tall  cylinder,  close  the  cylinder  and 
allow  the  insoluble  matter,  sodium  carbonate,  etc.,  to  settle.  The  clear 
liquid  will  be  practically  free  from  carbonate.  Dilute  it  in  the  proportion 
of  30  c.c.  to  -2  litres  of  water. 

Standard  Nitric  Acid. — Measure  2  litres  of  water  into  a  glass-stoppered 
bottle,  add  20  c.c.  of  nitric  acid  (1.42  sp.  gr.)  and  mix  thoroughly.  Measure 
accurately  10  c.c.  of  the  "  Standard  Solution  of  Sodium  Hydroxide." 
Place  them  in  a  small  flask,  add  40  c.c.  of  water  and  3  drops  of  "  Phenol- 
phthalein Solution."  Drop  "  Standard  Nitric  Acid"  from  a  carefully  cali- 
brated burette  into  the  flask  until  the  pink  color  just  disappears.  If  the 
solutions  are  not  of  the  same  strength,  dilute  the  stronger  with  water  until 
they  agree.  For  example,  if  it  required  9.5  c.c.  of  nitric  acid  to  discharge 
the  color,  return  the  nitric  acid  from  the  burette  to  the  bottle  and  dilute  it 
according  to  the  following  proportion:  9.5  :  10  =  2030  (the  volume  of 
nitric  acid  remaining)  :  2136.9. 

Add  106.9  c.c.  of  water  to  the  nitric  acid,  and  after  thoroughly  mixing 
it  retest  as  above. 

If  it  should  require  10.5  c.c.  of  the  nitric  acid  solution  to  discharge  the 
color,  dilute  the  sodium  hydroxide  solution  according  to  the  proportion : 
10  :  10.5  =  2010  (the  volume  of  sodium  hydroxide  remaining)  :  2110.5. 

Add  100.5  c-c-  °f  water  to  the  solution  of  sodium  hydroxide,  mix 
thoroughly,  and  retest. 


106  ANALYSIS   OF  IRON  AND   STEEL. 

The  standard  solutions  being  equal  in  strength,  standardize  them  as 
follows : 

Titrate  the  ammonium  phospho-molybdate  obtained  from  a  steel  in 
which  the  phosphorus  has  been  carefully  determined,  and  divide  the  per- 
centage of  phosphorus  by  the  number  of  c.c.  of  the  "  Standard  Solution  of 
Sodium  Hydroxide"  required  to  neutralize  it.  The  result  is  the  value  of 
the  "  Standard  Solution  of  Sodium  Hydroxide."  * 

Operation. 

Precipitate  the  ammonium  phospho-molybdate  from  2  grammes  of  the 
steel  exactly  as  described  in  the  last  method  "  Reduction  by  Zinc  and 
Titration  by  Permanganate  Solution." 

Filter  and  wash  first  with  "  Nitric  Acid  for  Washing  Precipitates"  and 
then  with  "  Potassium  Nitrate  Solution"  until  the  washings  are  no  longer 
acid.  Place  the  filter  and  precipitate  in  the  flask  in  which  the  precipitation 
was  made  and  run  in  from  a  pipette  10  c.c.  of  the  "Standard  Solution  of 
Sodium  Hydroxide."  If,  after  agitation,  this  is  insufficient  to  dissolve  the 
precipitate,  add  10  c.c.  more,  and  if  necessary  continue  the  additions  until 
the  precipitate  is  dissolved.  Dilute  to  50  c.c.,  add  3  drops  "  Phenol- 
phthalein  Solution,"  and  add  from  a  burette  "  Standard  Nitric  Acid"  until 
the  pink  color  disappears.  Subtract  the  number  of  c.c.  of  "  Standard 
Nitric  Acid"  used  from  the  number  of  c.c.  of  "  Standard  Solution  of 
Sodium  Hydroxide"  taken  to  dissolve  the  precipitate,  and  the  remainder 
will  be  the  number  of  c.c.  of  the  "  Standard  Solution  of  Sodium  Hydrox- 
ide" required  to  neutralize  the  ammonium  phospho-molybdate.  From 
this  calculate  the  amount  of  phosphorus  in  the  steel. 

Direct  Weighing1  of  the  Phospho-Molybdate. 

Instead  of  using  the  volumetric  method,  some  chemists  prefer  to 
weigh  the  yellow  precipitate.  Mr.  Wood's  method  f  is  as  follows : 

*  Mr.  Handy  prefers  to  have  the  solutions  of  such  strength  that  I  c.c.  =  0.0002  gramme  phos- 
phorus. To  obtain  this  result  calculate  the  weight  of  phosphorus  to  which  each  c.c.  of  the  solutions 
is  equivalent  and  dilute  them  as  required. 

|  Communicated  to  the  author.  Mr.  Wood  states  that  the  details  adapting  this  to  a  "rapid 
method"  were  worked  out  by  Mr.  J.  A.  Nichols,  of  the  Homestead  Works. 


RAPID   METHODS  FOR   PHOSPHORUS.  1 07 

Dissolve  1.63  grammes  steel  in  a  six-ounce  Erlenmeyer  flask  in 
30  c.c.  warm  nitric  acid  (1.2  sp.  gr.),  place  the  flask  over  a  Bunsen 
flame  and  evaporate  down  to  10  or  15  c.c.,  hastening  the  evaporation 
by  blowing  a  gentle  current  of  air  into  the  flask. 

Heat  50  c.c.  of  molybdate  solution  to  50°  or  55°  C,  add  it  to  the 
solution  in  the  flask,  and  shake  well.  Complete  precipitation  should 
take  place  in  from  three  to  five  minutes.  Filter  on  the  pump  in  a 
7  cm.  Munktell's  No.  I  filter  which  has  previously  been  washed,  dried 
at  1 00°  C.,  and  weighed.  Wash  with  dilute  nitric  acid,  suck  dry, 
wash  once  with  alcohol  and  thoroughly  with  ether,  and  place  the 
filter  containing  the  precipitate  in  a  funnel  in  an  air-bath  heated  to 
110°  C.  The  funnel  in  the  bath  is  connected  with  the  exhaust  so 
that  the  precipitate  and  filter  are  thoroughly  dried  in  from  one  to 
three  minutes,  according  to  the  size  of  the  precipitate.  Weigh,  and 
I  milligramme  of  the  precipitate  will  be  equal  to  .001  per  cent,  of 
phosphorus  in  the  steel. 

In  the  case  of  pig-iron  and  spiegel,  the  metal,  after  solution  in  nitric 
acid  (1.2  sp.  gr.),  is  diluted  with  20  c.c.  water,  5  drops  of  hydrofluoric 
acid  are  then  added,  the  solution  is  boiled  for  two  or  three  minutes, 
filtered  through  asbestos  on  the  pump,  and  concentrated  to  15  c.c. 

15  c.c.  of  chromic  acid  are  added,  the  solution  is  boiled  down  again  and 
precipitated  as  above.  The  hydrofluoric  acid  prevents  the  separation  of 
gelatinous  silica,  but  does  not  interfere  with  the  precipitation  of  phosphorus. 
This  method  will  not  work  with  ferro-manganese,  as  the  combined 
carbon  is  not  sufficiently  oxidized  and  prevents  the  precipitation  of 
all  the  phosphorus. 

The  solutions  referred  to  above  are  prepared  as  follows : 

Molybdic  acid  solution.  To  1200  c.c.  water  add  700  c.c.  ammonia 
(sp.  gr.  0.88)  and  one  pound  molybdic  acid;  when  the  molybdic  acid  is 
dissolved  add  300  c.c.  nitric  acid  (sp.  gr.  1.42),  and  cool.  Pour  this 
solution  into  a  mixture  of  4800  c.c.  water  and  2000  c.c.  concentrated 
nitric  acid.  Filter  for  use  after  standing  twenty-four  hours. 

Chromic  acid  solution:  1.42  sp.  gr.  nitric  acid  saturated  with 
chromic  acid. 


IO8  ANALYSIS   OF  IKON  AND   STEEL. 

DETERMINATION     OF    MANGANESE. 

The  Acetate  Method. 

Dissolve  I  gramme  of  drillings  in  15  c.c.  nitric  acid  (1.2  sp.  gr.)  in 
a  No.  2  Griffin's  beaker.  Evaporate  to  dryness  in  the  air-bath,  and 
heat  to  decompose  carbonaceous  matter.  Allow  the  beaker  to  cool, 
add  10  c.c.  hydrochloric  acid,  heat  carefully  until  all  the  ferric  oxide 
is  dissolved,  evaporate  to  dryness  to  get  rid  of  all  the  nitric  acid, 
redissolve  in  10  c.c.  hydrochloric  acid,  and  evaporate  carefully  until 
the  solution  is  almost  syrupy.  Dilute  with  cold  water  to  about 
IOO  c.c.,  and  filter  off  the  insoluble  matter,  allowing  the  filtrate 
and  washings  to  run  into  a  No.  6  Griffin's  beaker.  In  the  case  of 
steel  or  puddled  iron  the  filtration  may  be  omitted,  the  solution  being 
poured  into  the  large  beaker,  and  the  rinsings  of  the  small  beaker 
added.  To  the  solution  in  the  large  beaker,  which  should  amount 
to  about  200  c.c.,  add  a  solution  of  sodium  carbonate  very  slowly, 
stirring  vigorously.  The  solution  will  finally  become  very  dark  red 
in  color,  and  the  precipitate  formed  will  redissolve  very  slowly.  Add 
the  solution  of  sodium  carbonate  2  or  3  drops  at  a  time,  stir  well, 
and  allow  the  solution  to  stand  several  minutes,  to  see  whether  or 
not  the  precipitate  will  redissolve.  When,  under  these  circumstances, 
a  decided  precipitate  remains,  add  2  drops  of  hydrochloric  acid,  stir 
well,  and  allow  the  solution  to  stand  for  some  minutes;  if  the  solu- 
tion does  not  clear,  add  2  drops  more,  and  stir  again.  If  the  first 
part  of  the  operation  has  been  carefully  conducted,  this  amount  of 
hydrochloric  acid  will  usually  be  sufficient,  but  if,  for  any  reason,  too 
large  a  precipitate  has  been  formed,  it  may  require  a  few  drops  more. 
It  is  important,  however,  that  no  more  hydrochloric  acid  be  added  than 
just  enough  to  redissolve  the  precipitate  formed  by  the  sodium  car- 
bonate, and,  to  insure  this,  the  solution  should  be  well  stirred  and 
allowed  to  stand  a  sufficient  length  of  time  after  each  addition  of 
hydrochloric  acid.  The  solution  may  be  so  dark  in  color  that  it  is 
difficult  to  see  when  the  precipitate  does  finally  disappear,  but  by 


DETERMINATION  OF  MANGANESE.  1 09 

standing  the  beaker  on  a  piece  of  white  paper  the  light  reflected 
through  the  bottom  of  the  beaker  will  greatly  diminish  the  difficulty. 
When,  under  this  method  of  procedure,  the  solution  clears,  add  2 
grammes  of  sodium  acetate  dissolved  in  a  few  c.c.  of  water,  stir  well, 
and  dilute  the  solution  to  about  700  c.c.  with  boiling  water.  Heat 
it  to  boiling,  and  allow  it  to  boil  for  about  ten  minutes,  then  remove 
it  from  the  tripod,  and  allow  the  precipitated  ferric  hydrate  and  acetate 
to  settle.  Decant  the  clear,  supernatant  fluid  on  a  large  washed  filter, 
throw  the  precipitate  on,  and  wash  it  two  or  three  times  with  boiling 
water,  allowing  the  filtrate  to  run  into  a  large  beaker  or  flask,  from 
which  it  can  be  transferred  to  a  platinum  or  porcelain  dish  and 
evaporated  rapidly.  When  the  precipitate  has  drained  quite  dry,  by 
means  of  a  platinum  spatula  transfer  it  to  the  beaker  in  which  the 
precipitation  was  first  made ;  dissolve  the  precipitate  which  remains 
adhering  to  the  filter,  and  that  which  remains  on  the  blade  of  the 
spatula,  by  pouring  around  the  edge  of  the  filter  and  on  the  spatula 
held  over  it  10  c.c.  hydrochloric  acid  diluted  with  twice  its  vol- 
ume of  hot  water,  and  heat  the  beaker  containing  the  precipitate. 
Wash  the  filter  free  from  ferric  chloride  with  cold  water,  and  heat 
the  beaker  containing  the  precipitate  until  the  latter  is  dissolved. 
Cool  the  solution,  and  repeat  the  precipitation,  filtration,  and  reso- 
lution of  the  precipitate  precisely  as  in  the  first  case,  adding  this 
filtrate  to  the  first  one.  Precipitate,  filter,  and  wash  a  third  time  in 
the  same  manner,  evaporate  all  the  filtrates  together  until  they  are 
reduced  to  about  300  c.c.  in  volume,  and  transfer  this  solution  to  a 
No.  3  beaker. 

If  during  the  evaporation  any  manganese  has  become  oxidized  by  ex- 
posure to  the  air,  it  forms  a  hard  ring  on  the  side  of  the  capsule,  and  may 
be  dissolved,  after  the  solution  is  poured  into  the  beaker,  by  two  or  three 
drops  of  hydrochloric  acid,  and  washed  into  the  beaker.  Should  any 
ferric  oxide  separate  out,  pour  the  solution  in  the  capsule  through  a 
small  filter,  allowing  it  to  run  into  the  beaker,  wash  the  precipitate  with 
hot  water,  dissolve  it  in  a  very  few  drops  of  dilute  hydrochloric  acid,  and 
let  it  run  into  a  No.  I  beaker.  Add  just  enough  solution  of  sodium  car- 


1 10  ANALYSIS   OF  IRON  AND   STEEL. 

bonate  to  precipitate  it,  make  it  faintly  acid  with  acetic  acid,  boil  it,  and 
filter  into  the  main  solution. 

This  solution  now  contains  all  the  manganese,  nickel,  and  cobalt  and 
the  greater  part  of  the  copper  which  may  have  been  in  the  metal.  Add  to 
it  10  grammes  of  sodium  acetate  and  a  few  drops  of  acetic  acid,  heat  it  to 
boiling,  and  pass  a  current  of  hydrogen  sulphide  through  the  boiling  solu- 
tion for  fifteen  minutes.  This  will  precipitate  the  copper,  cobalt,  and  nickel. 
Filter  off  the  black  sulphides,  boil  the  filtrate  to  expel  the  excess  of 
hydrogen  sulphide,  let  the  solution  cool  somewhat,  and  add  bromine- 
water  in  excess.  If  no  precipitate  forms  at  first,  stand  the  solution,  which 
should  be  colored  by  the  bromine-water,  in  a  warm  place  for  an  hour  or 
two,  to  allow  the  precipitate  of  manganese  dioxide  to  separate  out.  If  a 
precipitate  forms  immediately,  add  bromine-water  until,  when  the  precipi- 
tate settles,  the  solution  is  strongly  colored  by  it,  and  stand  it  aside  for  an 
hour  or  two.  At  the  end  of  this  time,  the  precipitate  having  settled  and 
the  supernatant  fluid  being  still  colored  by  the  bromine,  heat  it  carefully, 
finally  to  boiling,  and  expel  the  excess  of  bromine ;  allow  the  precipitate 
to  settle,  filter,  wash  very  carefully,  and  avoid  stirring  up  the  precipitate 
when  it  is  on  the  filter,  as  it  has  a  tendency  to  go  through.  Dissolve  the 
precipitate  on  the  filter  in  sulphurous  acid  water  containing  a  little  hydro- 
chloric acid ;  allow  the  solution  to  run  into  a  platinum  dish,  and  wash  the 
filter  well.  A  little  of  the  sulphurous  acid  water  will  quickly  dissolve  any 
manganese  dioxide  which  may  adhere  to  the  beaker  in  which  it  was  precip- 
itated, and  this  may  be  poured  on  the  filter.  Boil  the  solution  in  the  dish  to 
expel  the  excess  of  sulphurous  acid,  add  from  5  to  20  c.c.  of  a  clear  filtered 
solution  of  microcosmic  salt,  heat  to  boiling,  and  add  ammonia,  drop  by 
drop,  with  constant  stirring.  When  the  precipitate  of  ammonium-man- 
ganese phosphate  begins  to  form,  stop  adding  ammonia,  and  stir  until  the 
precipitate  becomes  crystalline.  When  this  change  occurs,  add  one  more 
drop  of  ammonia;  the  additional  precipitate  formed  will  be  curdy,  but  a  few 
seconds'  continued  stirring  at  the  boiling  temperature  will  change  it  to  the 
silky  crystalline  condition.  Continue  the  addition  of  ammonia  in  exactly 
the  same  manner  until  the  precipitate  is  all  down  and  further  additions  of 
ammonia  fail  to  change  the  silky  appearance.  Add  a  dozen  drops  of 


DETERMINATION  OF  MANGANESE.  Ill 

ammonia  in  excess,  remove  the  dish  from  the  light,  and  stand  it  in  ice- 
water  until  perfectly  cold.  Filter  on  an  ashless  filter,  wash  with  cold  water 
containing  10  grammes  of  ammonium  nitrate  (dissolved  in  water  made 
faintly  alkaline  with  ammonia  and  filtered)  in  100  c.c.  until  the  filtrate  gives 
no  reaction  for  hydrochloric  acid,  dry,  ignite,  and  weigh  as  manganese 
pyrophosphate,  which  contains  38.74  per  cent,  manganese.  During  the 
precipitation  of  the  ammonium-manganese  phosphate  the  stirring  must  not 
be  discontinued  for  an  instant,  as  the  solution  has  a  great  tendency  to  bump 
when  the  precipitate  is  allowed  to  settle.  The  crystalline  condition  of  the 
precipitate,  which  is  absolutely  necessary  for  the  success  of  the  determi- 
nation, can  most  readily  be  brought  about  by  the  means  described  above. 
It  can,  of  course,  be  accomplished  by  adding  an  excess  of  ammonia  at 
once,  but  it  will  require  much  more  boiling  and  stirring  than  the  method 
above  described.  The  final  precipitation  as  ammonium-manganese  phos- 
phate, due  to  Dr.  Gibbs,  is  much  the  most  accurate  method  known.  A 
common  practice,  however,  is  to  wash  the  bromine  precipitate  of  hydrated 
manganese  dioxide,  dry,  ignite,  and  weigh  as  manganoso-manganic  oxide, 
which  contains  72.05  per  cent,  manganese.  There  are  two  objections  to 
this  method  of  procedure :  first,  the  difficulty  of  washing  the  manganese 
dioxide  free  from  sodium  salts ;  secondly,  the  uncertainty  as  to  the  exact 
state  of  oxidation  of  the  ignited  manganese  oxide. 

The  first  of  these  objections  Eggertz  claims  to  overcome  by  washing  the 
precipitated  manganese  with  water  containing  I  per  cent,  of  hydrochloric 
acid.  It  may  also  be  overcome,  or  rather  the  danger  may  be  avoided,  by 
using  no  fixed  alkalies.  By  this  method,  nearly  neutralize  the  hydro- 
chloric acid  solution  of  the  iron  or  steel  by  ammonia,  then  add  a  solution 
of  ammonium  carbonate  exactly  as  directed  above  for  sodium  carbonate, 
and  finally,  instead  of  sodium  acetate,  add  ammonium  acetate  (5  c.c. 
of  ammonia  slightly  acidulated  by  acetic  acid).  Evaporate  the  filtrates 
obtained  in  this  way  to  about  500  c.c.,  transfer  to  a  flask  of  about  I 
litre  capacity,  and  cool.  When  perfectly  cold,  add  3  or  4  c.c.  bromine, 
shake  well,  and  when  the  solution  is  strongly  colored  all  through  by  bro- 
mine, add  an  excess  of  ammonia,  and  heat  to  boiling.  Filter,  wash  with 
hot  water,  dry,  ignite,  and  weigh  as  manganoso-manganic  oxide. 


112  ANALYSIS   OF  IRON  AND   STEEL. 

The  second  objection  seems,  according  to  Pickering,*  to  be  well 
founded,  the  amount  of  manganese  in  the  ignited  oxides  varying  from 
69.688  per  cent,  to  74.997  per  cent.,  according  to  the  temperature  to  which 
they  were  heated  and  other  undetermined  conditions.  This  cause  of  error 
may  be  avoided  by  weighing  the  precipitate  as  manganous  sulphide,  con- 
taining 63.18  per  cent,  manganese.  This  method,  due  to  H.  Rose,f  is  car- 
ried out  as  follows.  Ignite  the  oxide  in  a  porcelain  crucible,  allow  it  to 
cool,  mix  it  with  five  or  six  times  its  volume  of  flowers  of  sulphur,  place 
the  crucible  on  a  triangle,  and  insert  the  bowl  of  a  clay  tobacco-pipe, 
which  should  be  large  enough  to  quite  fill  the  top  of  the  crucible  and  too 
large  to  reach  to  the  precipitate.  Pass  through  the  stem  a  current  of  dry 
hydrogen  until  all  air  is  expelled,  heat  the  crucible  gradually  to  as  high  a 
heat  as  a  good  Bunsen  burner  will  produce,  cool  in  the  current  of  hydro- 
gen, and  weigh  as  manganous  sulphide. 

General  Remarks  on  the  Acetate  Method. 

The  chief  source  of  error  in  the  acetate  method,  as  it  is  usually 
practised,  is  in  the  addition  of  too  much  sodium  acetate,  whereby  the 
manganous  chloride  is  changed  to  manganous  acetate,  which,  according 
to  Kessler,  J  is  readily  decomposed  to  manganous  oxide  and  acetic  acid. 
Under  these  circumstances,  a  larger  amount  of  manganese  is  precipitated 
with  the  iron  than  would  be  the  case  if  a  less  amount  of  sodium  acetate  were 
added.  When  sodium  acetate  is  added  to  ferric  chloride,  the  reaction  may 
be  written,  6NaC2H£>2.3H2O-f  Fe2Cl6  =  6NaCl  +  Fe2(C2H3O2)6  +  3H2O;  and 
to  precipitate  the  iron  as  ferric  acetate  in  I  gramme  of  metal  would  neces- 
sitate the  use  of  8  grammes  of  sodium  acetate.  But,  as  Kesslef  in  the 
same  article  remarks,  when  a  solution  of  ferric  chloride  is  treated  with 
sodium  carbonate  and  hydrochloric  acid  exactly  as  described  above,  a 
liquid  is  formed  which  contains  fourteen  times  its  equivalent  of  ferric 
hydrate  in  solution.  Consequently  ^  gramme  of  sodium  acetate  would 
be  sufficient  to  precipitate  I  gramme  of  iron  as  ferric  hydrate  and  basic 

*  Chem.  News,  xliii.  226.  f  Rose,  Quant.  Anal.  (French  ed. ),  p.  104. 

J  Chem.  News,  xxvii.  14. 


DETERMINATION  OF  MANGANESE.  113 

acetate.  In  order,  however,  to  precipitate  the  manganese  as  manganese 
dioxide  by  bromine,  it  is  necessary  to  convert  all  the  manganous  chloride 
into  manganous  acetate :  consequently  an  excess  of  sodium  acetate  is 
added  before  adding  bromine.  If,  when  making  the  acetate  precipitation, 
the  solution  contains  any  ferrous  chloride,  a  "  brick-dust"  precipitate  is 
usually  formed,  which  generally  passes  through  the  filter,  and  is  very  difficult 
to  dissolve  or  manage  in  any  way.  It  is  usually  the  shortest  and  best 
plan,  in  this  event,  to  start  a  fresh  portion  and  throw  away  the  other. 

The  Nitric  Acid  and  Potassium  Chlorate  Method. 

(Ford's  Method^ 

The  acetate  method  is  at  best  very  tedious,  and  when  the  amount  of 
manganese  is  very  small  it  is  of  course  desirable  to  work  on  larger 
amounts  than  I  gramme'  of  the  sample,  but  in  this  event  the  iron  precipi- 
tate is  so  large  that  it  becomes  very  difficult  to  manage  it  properly. 
With  Ford's  method  however,  there  is  almost  no  limit  to  the  amount 
which  can  be  operated  upon,  and  many  experiments  have  shown  that  with 
proper  precautions  it  is  an  extremely  accurate  process.  The  reaction  on 
which  the  process  is  based  was  first  noticed  by  Hannay  *  in  1878;  but 
Ford  t  first  worked  out  the  method  in  its  present  practical  form.  Dissolve 
5  grammes  of  borings  in  a  No.  3  beaker  in  60  c.c.  nitric  acid  (1.2  sp.  gr.), 
evaporate  down  until  the  solution  is  almost  syrupy,  then  add  100  c.c. 
strong  nitric  acid  (1.4  sp.  gr.)  and  5  grammes  potassium  chlorate.  Heat 
the  solution  to  boiling  either  on  the  hot  plate  or  on  a  tripod  with  a  thin 
piece  of  sheet  asbestos,  about  I  inch  (25  mm.)  in  diameter,  on  the  centre 
of  the  wire  gauze.  Boil  the  solution  fifteen  minutes,  remove  the  light, 
add  50  c.c.  strong  nitric  acid  and  5  grammes  potassium  chlorate,  replace 
the  light,  and  boil  fifteen  minutes  longer,  or  until  the  yellowish  fumes 
from  the  decomposition  of  the  potassium  chlorate  are  no  longer  given 
off.  Cool  the  solution  as  rapidly  as  possible  by  standing  the  beaker  in 
cold  water,  filter  on  the  pump,  using  the  cone  %  or  glass  filtering-tube 

*  Jour.  Chem.  Soc.,  xxxiii.  269.  f  Trans.  Inst.  Min.  Engineers,  ix.  397. 

J  See  page  27. 

8 


114  ANALYSIS   OF  IRON  AND   STEEL. 

with  asbestos  filter,*  and  wash  two  or  three  times  with  strong  nitric  acid, 
which  must  be  free  from  nitrous  fumes.f  Nitrous  acid  reduces  manganese 
dioxide  to  manganous  oxide,  which  then  dissolves  in  nitric  acid.  Its 
presence  may  be  recognized  by  the  yellow  color  it  imparts  to  nitric  acid, 
and  it  may  be  removed  by  blowing  air  through  the  acid.  It  is  always 
formed  in  nitric  acid  which  has  been  exposed  to  sunlight,  and  for  that 
reason  this  acid  should  be  kept  in  a  dark  place.  Suck  the  precipitate  dry, 
and  transfer  it,  with  the  asbestos  filter,  to  the  beaker  in  which  the  precipita- 
tion was  made.  Pour  into  the  beaker  from  10  to  40  c.c.  strong  sulphurous 
acid  water,  which  will  dissolve  the  precipitate  almost  instantly.  By  pour- 
ing it  through  the  cone  or  filtering-tube,  any  adhering  precipitate  will  be 
dissolved  and  carried  into  the  beaker.  As  soon  as  the  precipitate  is 
dissolved,  filter  from  the  asbestos  into  a  No.  I  beaker,  washing  with  hot 
water,  and  add  to  the  filtrate  from  2  to  5  c.c.  hydrochloric  acid.  Heat  the 
filtrate  until  the  excess  of  sulphurous  acid  is  driven  off,  add  bromine- 
water  until  the  solution  is  strongly  colored  with  it,  and  boil  ofT  the  excess 
of  bromine.  Add  ammonia  until  the  solution  smells  quite  strongly  of  it, 
boil  for  a  few  minutes,  and  filter  into  a  No.  3  beaker.  Wash  several  times 
with  hot  water,  remove  the  beaker,  dissolve  the  ferric  hydrate  on  the  filter 
in  dilute  hot  hydrochloric  acid  (i  part  of  acid  to  3  of  water),  allowing  the 
solution  to  run  back  into  the  beaker  in  which  the  precipitation  was  made, 
and  wash  the  filter  with  hot  water.  Boil  this  filtrate  for  a  few  minutes  to 
drive  off  the  chlorine  which  may  be  present  from  the  solution  of  any  lithe 
manganese  dioxide  precipitated  with  the  ferric  hydrate,  reprecipitate  by 
ammonia  as  before,  filter,  and  repeat  the  solution,  precipitation,  and  filtra- 
tion, allowing  all  the  filtrates  from  the  ferric  hydrate  to  run  into  the  No.  3 
beaker.  •  Acidulate  this  solution,  which  will  be  about  300  or  400  c.c.  in 
volume,  with  acetic  acid,  heat  to  boiling,  and  pass  hydrogen  sulphide 
through  the  boiling  solution  for  ten  or  fifteen  minutes.  Filter  into  a 
platinum  dish  from  any  cobalt  sulphide,  which  is  the  only  metal  likely  to  be 

*  As  described  under  Methods  for  Determination  of  Carbon. 

f  It  is  always  well  to  transfer  the  filtrate  and  washings  to  a  No.  4  beaker,  add  2  grammes 
potassium  chlorate,  and  boil  again,  to  see  whether  any  further  precipitate  of  manganese  dioxide  is 
formed. 


DETERMINATION  OF  MANGANESE.  1 15 

present  with  the  manganese ;  boil  off  the  hydrogen  sulphide  after  adding 
a  little  hydrochloric  acid,  add  microcosmic  salt,  and  precipitate,  filter,  ignite, 
and  weigh,  as  directed  on  pages  1 10  and  1 1 1,  as  manganese  pyrophosphate. 


Steels  containing  much  Silicon. 

In  steel  high  in  silicon  (0.2  per  cent,  and  over)  the  gelatinous  silica 
formed  is  very  apt  to  clog  the  filter  when  operating  as  described  above,  and 
it  is  better  to  dissolve  the  sample  in  hydrochloric  acid,  evaporate  to  dryness, 
being  careful  not  to  heat  it  too  hot,  redissolve  carefully  in  50  c.c.  strong 
nitric  acid,  boil  down  until  nearly  syrupy  to  destroy  all  the  hydrochloric 
acid,  redissolve  in  100  c.c.  strong  nitric  acid,  and  precipitate  as  directed 
above. 

Instead  of  dissolving  in  hydrochloric  acid,  Mr.  Wood  suggests  adding 
a  few  drops  of  hydrofluoric  acid  to  the  nitric  acid  solution  before  evapo- 
rating. This  seems  to  work  extremely  well,  and  saves  much  time  in  the 
case  of  high  silicon  steels.  It  may  also  be  used  to  advantage  in  the  case 
of  pig-iron  instead  of  the  method  given  below. 

Pig-iron. 

Dissolve  5  grammes  in  50  c.c.  dilute  hydrochloric  acid  (i  part  hydro- 
chloric acid  to  I  part  water),  filter  on  a  washed  filter  into  a  No.  3  beaker, 
evaporate  to  dryness,  redissolve  in  50  c.c.  strong  nitric  acid,  and  proceed 
as  in  the  case  of  "  steel  high  in  silicon." 

Spiegel  and  Ferro-manganese. 

It  is  best  to  use  only  I  gramme  of  spiegel  or  ferro-manganese  of  from 
20  to  40  per  cen-t.  manganese  and  .5  gramme  or  y^-factor  weight  of  very 
high  (from  60  to  80  per  cent.)  ferro-manganese.  In  the  latter,  indeed,  it  is 
better  to  use  the  acetate  method  with  ammonia  and  acetic  acid,  and, 
omitting  the  precipitation  by  bromine,  boil  off  the  hydrogen  sulphide 
from  the  filtrate  from  the  insoluble  sulphides,  after  adding  hydrochloric 
acid,  and  then  precipitate  by  microcosmic  salt  as  directed  above. 


Il6  ANALYSIS   OF  IRON  AND   STEEL. 

RAPID    METHODS. 

Volumetric  Methods. 
Volhard's  Method* 

This  method  is  based  on  the  principle  announced  by  Morawski  and 
Stingl.f  that  when  potassium  permanganate  is  added  to  a  neutral  manga- 
nous  salt  all  the  manganese  is  precipitated,  in  accordance  with  the  reaction 
4KMnO4  +  6MnSO4  +  4H2O  =  ioMnO2  +  4KHSO,  +  2H2SO4.  When  all 
the  manganous  salt  is  oxidized,  the  solution  is  colored  by  the  permanganate, 
which  thus  indicates  the  end  reaction.  The  permanganate  used  for  titrating 
iron  ores  may  be  used  for  this  determination,  and,  its  value  being  deter- 
mined, as  directed,  in  terms  of  iron,  the  calculation  for  manganese  is  as 
follows.  The  reaction,  when  permanganate  is  added  to  a  solution  of  fer- 
rous sulphate,  is  ioFeSO4-h 2KMnO4+8H,SO4=5Fe2(SO4)s  +  2MnSO4  + 
K2SO4  +  8H2O,  or  2  molecules  of  potassium  permanganate  oxidize  10 
molecules  of  ferrous  sulphate.  Now,  as  2  molecules  of  permanganate 
oxidize  3  molecules  of  manganous  sulphate,  while  2  molecules  of  perman- 
ganate oxidize  10  molecules  of  ferrous  sulphate,  the  oxidizing  power  of  the 
permanganate  is  only  three-tenths  as  great  in  the  former  case  as  it  is  in 
the  latter,  and  its  value  in  manganese  is  to  its  value  in  iron  as  3  is  to  10, 
or  -ff  X  T8tf  =  iff-  Therefore  the  value  of  the  permanganate  in  iron 
multiplied  by  -§-££  or  0.2946  —  its  value  in  manganese. 

Dissolve  1.5  grammes  of  borings  in  a  platinum  or  porcelain  dish  in 
25  c.c.  nitric  acid  (1.2  sp.  gr.).  When  solution  is  complete,  add  12  c.c. 
dilute  sulphuric  acid  (i  part  concentrated  sulphuric  acid  and  I  part  water), 
and  evaporate  to  dryness,  as  directed  on  page  20,  heating  until  fumes  of 
sulphuric  acid  are  given  off  in  order  to  destroy  all  the  carbonaceous 
matter.  Or  dissolve  in  nitric  acid  as  above,  evaporate  to  dryness, 
and  heat  on  the  tripod  until  the  carbonaceous  matter  is  destroyed ; 
dissolve  in  15  c.c.  hydrochloric  acid,  add  12  c.c.  dilute  sulphuric  acid 
as  above,  and  evaporate  until  fumes  of  sulphuric  acid  are  given  off. 

*  Liebig's  Annalen,  cxcviii.  318  ;  Chem.  News,  xl.  207. 
|  Chem.  News,  xxxviii.  297. 


RAPID   METHODS  FOR   MANGANESE.  117 

Allow  the  dish  to  cool,  add  100  c.c.  water,  and  heat  until  the  ferric 
sulphate  is  dissolved.  Wash  into  a  carefully  graduated  300  c.c.  flask, 
so  that  with  the  washings  the  solution  may  not  exceed  200  c.c.  in 
volume,  and  add  a  solution  of  sodium  carbonate  until  the  precipitate 
which  is  first  formed  dissolves  only  with  difficulty.  Then  add  slowly 
zinc  oxide  *  suspended  in  water,  shaking  well  after  each  addition  until 
the  iron  is  precipitated,  which  will  be  shown  by  the  sudden  coagulation 
of  the  solution.  The  precipitate  will  then  settle,  leaving  a  slightly 
milky  supernatant  liquid.  Fill  the  flask  exactly  to  the  mark  on  the 
neck  (300  c.c.),  and  mix  thoroughly  by  pouring  the  entire  contents 
of  the  flask  into  a  large,  clean,  dry  beaker,  and  back  again  into  the 
flask,  repeating  this  several  times.  Allow  the  precipitate  to  settle  for 
a  few  minutes,  and  pour  the  solution  through  a  large,  dry  filter.  Fill 
a  200  c.c.  pipette  with  this  filtrate,  which  will,  of  course,  represent 
exactly  I  gramme  of  the  sample,  run  it  into  a  flask  of  about  500  c.c. 
capacity,  heat  to  boiling,  and  add  from  2  to  5  drops  of  nitric  acid  (sp.  gr. 
\.2\  Now  add  permanganate  solution  slowly  from  a  burette,  shaking 
after  each  addition  to  mix  the  solution  and  facilitate  the  collection  of 
the  precipitated  hydrated  manganese  dioxide.  When  the  reaction  is 
nearly  finished,  the  solution  will  be  slightly  colored  by  the  perman- 
ganate, but  the  color  disappears  after  shaking  the  flask  and  allowing 
it  to  stand  for  a  moment.  Finally,  however,  a  drop  or  two  will  give 
the  solution  a  permanent  pink  color,  which  will  not  disappear  for 
several  minutes.  The  number  of  c.c.  of  the  permanganate  solution 
used  multiplied  by  the  factor  found  (the  iron  factor  of  the  perman- 
ganate multiplied  by  0.2946)  is  the  amount  of  manganese  in  the 
sample.  If,  during  the  addition  of  the  permanganate,  the  solution 
should  become  cool  and  the  precipitate  fail  to  collect  and  settle 
quickly,  heat  the  solution,  but  not  quite  to  the  boiling-point.  This 
method  is  applicable  for  all  samples  except  those  containing  very 
minute  amounts  of  manganese.  In  working  on  spiegel,  take  .75 
gramme,  then,  using  two-thirds  of  the  filtrate,  the  amount  will  be 
calculated  on  .5  gramme. 

*  See  page  58. 


Il8  ANALYSIS   OF  IRON  AND   STEEL. 

Williams  s  Method. 

This  method,  which  consists  in  precipitating  the  manganese  dioxide 
by  Ford's  method,  filtering,  washing,  dissolving  in  sulphuric  acid  with 
a  measured  volume  of  some  reducing  agent,  such  as  oxalic  acid  or 
ferrous  sulphate,  and  titrating  the  excess  by  permanganate,  was  first 
used  by  Williams.*  Regarding  the  precipitate  by  potassium  chlorate 
in  a  nitric  acid  solution  as  manganese  dioxide,  the  reaction  in  dis- 
solving it  might  be  expressed  thus:  MnO2  +  2FeSO4  -f  2H2SO4  - 
MnSO4  +  Fe2(SO4)3  +  2H2O,  or  MnO2  +  H2C2O4  +  H2SO4  =  MnSO4  + 
2CO2-(-2H2O.  Therefore  I  molecule  of  manganese  dioxide  oxidizes 
2  molecules  of  ferrous  sulphate  or  I  molecule  of  oxalic  acid,  and,  the 
excess  of  oxalic  acid  or  ferrous  sulphate  unoxidized  having  been 
determined  by  a  solution  of  permanganate,  the  difference  between 
this  excess  and  the  amount  originally  added  is  the  amount  oxidized 
by  the  manganese  dioxide. 

We  therefore  require  two  standard  solutions,  one  of  permanganate  and 
one  of  ferrous  sulphate,  ammonium-ferrous  sulphate,  or  oxalic  acid.  The 
permanganate  solution  used  for  iron  determinations  answers  perfectly.  A 
solution  of  ferrous  sulphate  is  perhaps  the  most  satisfactory,  and  is  pre- 
pared by  dissolving  10  grammes  of  the  crystallized  salt,  FeSO4,/H2O,t  in 
900  c.c.  water  and  100  c.c.  strong  sulphuric  acid.  It  will  keep  perfectly  in 
a  glass-stoppered  bottle  in  the  dark  for  a  long  time.  One  c.c.  of  this 
solution  will  be  equal  to  about  .002  gramme  iron,  or  nearly  .001  gramme 
manganese,  and  if  the  permanganate  is  of  the  usual  strength,  say  I  c.c.  = 
.007  gramme  iron,  I  c.c.  of  the  permanganate  will  equal  about  3.5  c.c.  of 
the  ferrous  sulphate.  The  permanganate  solution  having  been  carefully 
standardized,  transfer  50  c.c.  of  the  ferrous  sulphate  solution  by  means  of  a 
pipette  to  a  dish,  dilute  to  about  I  litre,  and  run  in  permanganate  solution 
from  a  burette,  stirring  constantly  until  the  first  permanent  pink  tint  appears. 
The  reading  of  the  burette  will  give  the  value  of  50  c.c.  ferrous  sulphate  in 
permanganate,  and  consequently  by  a  simple  calculation  its  value  in  iron  and 
manganese.  Suppose,  for  instance,  I  c.c.  permanganate  solution  =.0068 


Trans.  Inst.  Min.  Engineers,  x.  100.  f  See  page  56. 


RAPID   METHODS  FOR   MANGANESE. 


FIG.   54. 


gramme  iron,  or  (according  to  the  proportion  given  above,  112  :  55  :  :  iron: 
manganese)  =.00334  gramme  manganese.  Then  if  14.1  c.c.  permanganate 
=  50  c.c.  ferrous  sulphate,  100  c.c.  ferrous  sulphate  will  be  equivalent  to 
28.2  c.c.  permanganate.  In  using  oxalic  acid,  dissolve  2.25  grammes  of 
the  crystallized  acid,  H2C2O4,2H2O,  in  I  litre  of  water,  and  determine  its 
strength  by  pouring  50  c.c.  into  the  dish,  diluting  with  hot  water,  adding 
5  c.c.  sulphuric  acid,  and  titrating  with  permanganate. 

The  details  of  the  method  are  as  follows.  Weigh  out  5  grammes  of 
the  sample  of  puddled  iron,  pig-iron,  or  steel,  and  proceed  as  directed  on 
page  113  et  seq. ;  but  after  filtering  and 
washing  the  precipitated  manganese  diox- 
ide with  strong  nitric  acid,  suck  the  pre- 
cipitate as  dry  as  possible,  and  then  wash 
out  the  beaker  in  which  the  precipitation 
was  made  with  cold  water.  Pour  this 
water  on  the  precipitate,  and  repeat  the 
operation  two  or  three  times  to  get  rid  of 
all  the  nitric  acid.  Suck  the  precipitate 
as  dry  as  possible,  transfer  it  with  the  as- 
bestos to  the  beaker  in  which  the  precipi- 
tation was  made,  measure  into  the  beaker 
100  c.c.  of  the  standard  ferrous  sulphate 
solution  (or  100  c.c.  oxalic  acid  solution 
and  10  c.c.  sulphuric  acid),  and  stir  until 
the  manganese  dioxide  is  all  dissolved. 
When  using  oxalic  acid  it  is  necessary  to 

heat  gently  to  about  60°  C.  Wash  the  solution  and  abestos  into  the  dish, 
dilute  to  about  I  litre  (with  oxalic  acid  use  hot  water),  and  titrate  with 
permanganate.  We  will  suppose,  for  example,  that  it  requires  io.2  c.c. 
permanganate  to  give  the  permanent  rose  tint;  then,  as  100  c.c.  ferrous 
sulphate  =  28.2  c.c.  permanganate,  there  would  be  the  equivalent  of 
28.2 — 10.2=  1 8  c.c.  permanganate  in  ferrous  sulphate  oxidized  by  the 
manganese  dioxide  precipitate.  One  c.c.  of  permanganate  being  equiv- 
alent to  .00334  gramme  manganese,  18  c.c.  =  . 06012  gramme  manganese, 


I  2O  ANAL  YSIS   OF  IRON  AND   STEEL. 

and,  5  grammes  of  the  sample  having  been  taken,  .06012  -r-  5  =0.01202 
X  100  =  1. 202  per  cent,  manganese. 

Fig.  54  shows  a  very  convenient  piece  of  apparatus  designed  by  Mr. 
E.  A.  Uehling  in  1884.* 

It  is  especially  useful  when  it  is  necessary  to  add  rapidly  a  constant 
volume  of  a  standard  reagent ;  for  instance,  a  measured  excess  of  ferrous 
sulphate  in  volumetric  determination  of  manganese  after  precipitation  with 
potassium  chlorate. 

The  burette-tube  extends  to  the  bottom  of  the  Wolff  bottle,  which 
holds  2  litres.  Enough  air  is  supplied,  without  danger  of  dust  or  evapora- 
tion of  solution,  by  means  of  a  pin-hole  drilled  in  the  neck  of  the  bottle 
and  through  the  hollow  glass  stopper.  The  bottle  may  be  blackened  to 
preserve  the  solution  from  the  action  of  light. 

Spiegel  and  Ferro-manganese . 

When  working  on  Spiegel  or  ferro-manganese,  take  .5  gramme  of  the 
sample  and  proceed  in  the  same  manner  as  directed  for  steel  or  iron ;  but 
it  is  better  to  use  a  standard  solution  of  ferrous  sulphate  containing  30 
grammes  of  FeSO^./H^O  to  the  litre  for  very  high  ferro-manganese. 

As  there  seems  to  be  some  uncertainty  as  to  the  exact  composition 
of  the  manganese  oxide,f  the  permanganate  solution  may  be  standardized 
as  follows.  Determine  the  absolute  amount  of  manganese  in  a  finely 
ground  and  well-mixed  sample  of  Spiegel  or  ferro-manganese  by  a  gravi- 
metric method,  then  treat  .5  gramme  of  the  same  sample  exactly  as  de- 
scribed above,  and,  having  found  the  number  of  c.c.  of  permanganate  that 
are  equivalent  to  100  c.c.  of  the  ferrous  sulphate  solution,  the  amount  of 
manganese  in  the  sample  divided  by  the  number  of  c.c.  of  permanganate 
equivalent  to  the  ferrous  sulphate  oxidized  by  the  manganese  oxide  in  the 
sample  gives  the  value  of  the  permanganate  solution.  Thus,  if  100  c.c. 
ferrous  sulphate  solution  require  28.2  c.c.  permanganate  to  give  the  rose 
tint  upon  titration,  the  sample  of  spiegel  contains  14.50  per  cent,  manganese, 

*  Communicated  to  the  author  by  Mr.  A.  L.  Colby,  of  the  Bethlehem  Iron  Company. 
f  Stone,  Trans.   Inst.  Min.   Engineers,  xi.  323,  xii.  295,  514;  Mackintosh,  Trans.  Inst.   Min. 
Engineers,  xii.  79,  xiii.  39. 


RAPID   METHODS  FOR  MANGANESE.  121 

and  the  ferrous  sulphate  remaining  after  the  solution  of  the  manganese 
oxide  in  100  c.c.  requires  6.5  c.c.  permanganate  to  give  the  rose  tint  upon 
titration  (using  .5  gramme  of  the  sample,  of  which  I  gramme  contains 
.1450  gramme  manganese),  the  calculation  would  be  as  follows:  28.2  c.c. 
—  6.5  c.c.  =  21.7  c.c.  =  .0725  gramme  manganese,  or  I  c.c.  permanganate 
is  equivalent  to  -^-^=.00334  gramme  manganese. 

Bismuthate  Method. 

This  method  was  originally  proposed  by  Schneider,*  and  modified  first 
by  Reddrop  and  Ramage,f  and  then  by  Brearley  and  Ibbotson.J 

The  method  was  based  on  the  fact  that  a  manganous  salt  in  the  presence 
of  an  excess  of  nitric  acid  is  oxidized  to  permanganic  acid  by  bismuth 
tetroxide.  The  permanganic  acid  formed  is  very  stable  in  nitric  acid  of 
1.135  sp.  gr.,  when  the  solution  is  cold,  but  in  hot  solutions  the  excess  of 
the  bismuth  tetroxide  is  rapidly  decomposed,  and  then  the  nitric  acid  reacts 
with  the  permanganic  acid,  and,  as  soon  as  a  small  amount  of  manganous 
salt  is  formed,  the  remainder  of  the  permanganic  acid  is  decomposed,  man- 
ganous nitrate  dissolves,  and  manganese  dioxide  precipitates. 

In  the  cold,  however,  the  excess  of  the  bismuth  salt  may  be  filtered  off, 
and  to  the  clear  filtrate  an  excess  of  ferrous  sulphate  added,  and  the  amount 
necessary  to  deoxidize  the  permanganic  acid  determined  by  titrating  with 
permanganate.  The  end  reactions  are  very  sharp  and  the  method  is  ex- 
tremely accurate,  but  the  presence  of  even  traces  of  hydrochloric  acid  utterly 
vitiates  the  results.  As  pointed  out  by  Reddrop  and  Ramage,  bismuth 
tetroxide  which  was  used  by  Schneider  is  difficult  to  obtain  free  from  chlo- 
rides, and  they  recommended  sodium  bismuthate,  which  they  prepare  as 
follows :  Heat  20  parts  of  caustic  soda  nearly  to  redness  in  an  iron  or 
nickel  crucible,  and  add,  in  small  quantities  at  a  time,  10  parts  of  basic 
bismuth  nitrate,  previously  dried  in  a  water-oven.  Then  add  2  parts  of 
sodium  peroxide  and  pour  the  brownish-yellow  fused  mass  on  an  iron 
plate  to  cool ;  when  cold,  break  it  up  in  a  mortar,  extract  with  water,  and 

*  Ding.  poly.  J.,  269,  224.  f  Trans.  Chem.  Soc.,  1895,  p.  268. 

\  "  The  Analysis  of  Steel  Works  Materials." 


122  ANAL  YSIS  OF  IRON  AND  STEEL. 

collect  on  an  asbestos  filter.  The  residue,  after  being  washed  four  or  five 
times  by  decantation,  is  dried  in  the  water-oven,  then  broken  up  and  passed 
through  a  fine  sieve. 

The  Method. 

Steels. — Dissolve  I  gramme  of  drillings  in  50  c.c.  of  nitric  acid  (sp.  gr. 
1.135)  in  an  Erlenmeyer  flask  of  200  c.c.  capacity.  Cool,  and  add  about  0.5 
gramme  of  bismuthate.  The  bismuthate  may  be  measured  in  a  small  spoon, 
and  experience  will  soon  enable  the  operator  to  judge  of  the  amount  with 
sufficient  accuracy.  Heat  for  a  few  minutes,  or  until  the  pink  color  has  dis- 
appeared, with  or  without  the  precipitation  of  manganese  dioxide.  Add 
sulphurous  acid,  solution  of  ferrous  sulphate,  or  sodium  thiosulphate,  in 
sufficient  amount  to  clear  the  solution,  and  heat  until  all  nitrous  oxide  has 
been  driven  off.  Cool  to  about  15°  C,  add  an  excess  of  bismuthate,  and 
agitate  for  a  few  minutes.  Add  50  c.c.  of  water  containing  30  c.c.  of  nitric 
acid  to  the  litre,  and  filter  through  an  asbestos  felt  on  a  platinum  cone  into 
a  300  c.c.  Erlenmeyer  flask  and  wash  with  50  to  100  c.c.  of  the  same  acid. 
The  arrangement  shown  in  Fig.  55  has  proved  very  satisfactory.  Run  into 
the  flask  from  the  pipette,  shown  in  Fig.  56,  a  measured  volume  of  ferrous 
sulphate  solution  and  titrate  to  a  faint  pink  color  with  permanganate.  The 
number  of  cubic  centimetres  of  the  permanganate  solution  obtained,  sub- 
tracted from  the  number  corresponding  to  the  volume  of  ferrous  sulphate 
used,  will  give  the  volume  of  permanganate  equivalent  to  the  manganese 
in  the  sample,  which,  multiplied  by  the  value  of  the  permanganate  in 
manganese,  gives  the  amount  of  manganese  in  the  steel. 

Pig  Iron. — Dissolve  one  gramme  in  25  c.c.  of  nitric  acid  (sp.  gr.  1.135)  in 
a  small  beaker  and,  as  soon  as  the  action  has  ceased,  filter  on  a  7  cm.  filter 
into  a  200  c.c.  Erlenmeyer  flask,  wash  with  30  c.c.  of  the  same  acid,  and 
proceed  as  in  the  case  of  steels. 

In  the  analysis  of  white  irons  it  may  be  necessary  to  treat  the  solution 
several  times  with  bismuthate  to  destroy  the  combined  carbon.  The 
solution,  when  cold,  should  be  nearly  colorless ;  if  not,  another  treatment 
with  bismuthate  is  necessary. 


RAPID  METHODS  FOR  MANGANESE. 


'23 


Iron  Ores  Containing  less  than  2  Per  Cent,  of  Manganese. — Treat  I 
gramme  in  a  platinum  dish  or  crucible  with  4  c.c.  of  strong  sulphuric  acid,  10 
c.c.  of  water,  and  10  to  20  c.c.  of  hydrofluoric  acid.  Evaporate  until  the  sul- 
phuric acid  fumes  freely.  Cool  and  dissolve  in  25  c.c.  of  1.135  nitric  acid. 


FIG.  56. 


FIG.  55. 


If  no  appreciable  residue  remains,  transfer  to  a  200  c.c.  Erlenmeyer  flask, 
using  25  c.c.  of  1.135  nitric  acid  to  rinse  the  dish  or  crucible,  and  proceed 
as  usual.  If  there  is  an  appreciable  residue,  filter  on  a  small  filter  into  a 
beaker,  wash  with  water,  burn  the  filter  and  residue1  in  a  crucible,  and  fuse 


I  24  ANAL  YSIS  OF  IRON  AND  STEEL. 

with  a  small  amount  of  potassium  bisulphate.  Dissolve  in  water,  with  the 
addition  of  a  little  nitric  acid,  add  to  the  main  filtrate,  evaporate  nearly  to 
dryness,  take  up  in  1.135  nitric  acid,  and  transfer  to  the  flask  as  before. 

Manganese  Ores  and  Iron  Ores  Pligh  in  Manganese. — Treat  I  gramme  as 
in  case  of  iron  ores,  using  a  little  sulphurous  acid,  if  necessary.  Transfer 
the  solution  to  a  500  c.c.  flask,  dilute  to  the  mark,  mix  thoroughly,  and 
measure  into  the  flask  from  a  carefully  calibrated  pipette  such  a  volume 
of  the  solution  as  will  give  from  I  to  2  per  cent,  of  manganese  and 
enough  strong  nitric  acid  (sp.  gr.  1.4)  to  yield  a  mixture  of  1.135  acid 
in  a  volume  of  50  to  60  c.c.  For  example,  in  a  50  per  cent,  ore  use 
10  c.c.  of  the  solution  and  add  30  c.c.  of  water  and  10  c.c.  nitric  acid 
(sp.  gr.  1.4).  In  this  case,  the  manganese  must  be  calculated  on  ^  of  a 
gramme  or  20  mg.  of  ore.  When  working  on  such  amounts  it  is  always 
desirable  to  make  duplicate  analyses  and  take  the  mean,  as  a  difference 
of  O.I  c.c.  makes  a  large  error  in  the  result.  When  the  ore  contains  a 
much  smaller  amount  of  manganese,  say  5  or  10  per  cent,  it  is  better 
to  make  up  the  solution  to  say  100  c.c.  instead  of  500. 

Ferro-manganese. — Treat  I  gramme  exactly  like  steel.  Dilute  to  500  or 
1000  c.c.  and  proceed  as  in  manganese  ores. 

Ferro- silicon. — Treat  I  gramme  with  sulphuric  and  hydrofluoric  acids 
and  proceed  as  with  iron  ores. 

Special  Steels. — Steels  containing  chromium  offer  no  special  difficulties, 
except  that  it  must  be  noted  that  while  in  hot  solutions  the  chromium  is 
oxidized  to  chromic  acid,  which  is  reduced  by  the  addition  of  sulphurous 
acid,  the  oxidation  proceeds  so  slowly  in  cold  solutions  that  if  there  is  no 
delay  in  the  filtration  and  titration  the  results  are  not  affected.  Steels  con- 
taining tungsten  are  sometimes  troublesome  on  account  of  the  necessity 
for  getting  rid  of  the  tungstic  acid.  Those  that  decompose  readily  in  nitric 
acid  may  be  filtered  and  the  filtrate  treated  like  pig  iron,  but  when  it  is 
necessary  to  use  hydrochloric  acid  it  is  best  to  treat  with  aqua  regia, 
evaporate  to  dryness,  redissolve  in  hydrochloric  acid,  add  a  few  drops 
of  nitric  acid,  dilute,  boil,  and  filter.  Get  rid  of  every  trace  of  hydro- 
chloric acid  by  repeated  evaporations  with  nitric  acid,  and  proceed  as 
with  an  ordinary  steel. 


RAPID  METHODS  FOR  MANGANESE.  12$ 

Reagents. 

Nitric  Acid  (sp.  gr.  1.135). — A  mixture  of  3  parts  of  water  and  I  part 
strong  nitric  acid  answers  perfectly  for  this  purpose. 

Nitric  Acid  (3  percent). — Thirty  c.c.  of  strong  nitric  acid  to  the  litre. 

Permanganate  Solution  and  Ferrous  Sulphate  Solution. — One  gramme  of 
potassium  permanganate  to  the  litre  gives  a  solution  of  convenient  strength, 
and  12.4  grammes  of  ferrous  ammonium  sulphate  and  50  c.c.  of  strong 
sulphuric  acid,*  made  up  to  I  litre,  give  a  solution  which  is  almost  exactly 
equal  to  the  permanganate  solution.  As  the  strength  of  the  ferrous  sul- 
phate solution  changes  quite  rapidly,  while  the  permanganate  remains 
unaltered  for  months,  it  is  unnecessary  and  troublesome  to  keep  them  of 
the  same  strength.  By  using  a  constant  volume  of  the  ferrous  sulphate 
solution  and  testing  it  against  the  permanganate  solution  every  day,  the 
calculation  of  the  results  is  very  simple.  It  is  necessary  that  the  condi- 
tions should  be  the  same  in  getting  the  strength  of  the  ferrous  sulphate 
solution  as  in  titrating  a  solution  for  manganese,  and  after  many  experi- 
ments the  following  method  of  procedure  was  adopted :  Measure  into  a 
200  c.c.  flask  50  c.c.  of  nitric  acid  (sp.  gr.  1.135),  cool,  and  add  a  very  small 
amount  of  bismuthate,  dilute  with  50  c.c.  of  3  per  cent,  nitric  acid,  filter 
into  a  300  c.c.  flask,  and  wash  with  50  c.c.  of  3  per  cent,  nitric  acid.  If  the 
felt  is  well  coated  with  bismuthate  it  is  unnecessary  to  add  any  to  the 
nitric  acid  in  the  flask,  as  filtration  through  the  mass  of  bismuthate  on  the 
felt  will  answer  the  purpose.  Run  in  from  the  pipette  (Fig.  56)  25  c.c. 
of  ferrous  sulphate  solution  and  titrate  with  the  permanganate  to  a  faint 
pink.  This  gives  the  value  in  permanganate  of  the  ferrous  sulphate 
solution.  With  this  method  of  procedure  the  discrepancies  that  had 
occurred  entirely  disappeared,  and  it  is  possible  to  make  any  number  of 
determinations  with  a  variation  of  less  than  o.i  c.c. 

The  permanganate  solution  may  be  standardized  in  three  ways: 

First,  by  getting  its  value  in  iron,  in  the  usual  way,  and  calculating  its 

*  Dr.   C.   B.    Dudley  proposes  to  use  25  c.c.   of  sulphuric  and  25  c.c.  of  strong  phosphoric 
acid  as  tending  to  give  a  more  nearly  colorless  solution. 


1 26  ANAL  YSIS  OF  IRON  AND  STEEL. 

value  in  manganese.  The  proportion  is  280  :  55  or  as  i  :  0.19643,  or  taking 
the  atomic  weight  of  iron  as  5 5. 9  the  proportion  would  be  279.5  :  55=0.1968. 

Second,  by  titrating  a  steel  containing  a  known  amount  of  manganese 
and  getting  the  value  of  the  solution  by  dividing  the  percentage  of  man- 
ganese by  the  number  of  cubic  centimetres  of  the  permanganate  used. 

Third,  by  making  a  solution  of  pure  manganese  sulphate  and  determin- 
ing the  manganese  in  it  by  evaporating  a  weighed  amount  of  the  solution  to 
dryness,  heating  to  dull  redness,  and  weighing  as  manganese  sulphate,  which, 
multiplied  by  0.36424,  gives  the  amount  of  manganese.  Five  grammes 
of  "  C.P."  manganese  sulphate  dissolved  in  500  c.c.  of  water  and  filtered 
will  give  a  solution  containing  about  0.0035  gramme  of  manganese  to  the 
gramme  of  solution.  Weigh  I  to  3  grammes  of  the  solution  in  a  crucible, 
transfer  to  a  200  c.c.  flask,  using  50  c.c.  of  nitric  acid  (sp.  gr.  1.135),  cool, 
add  0.5  to  i  gramme  bismuthate,  and  allow  it  to  stand  for  three  or  four 
minutes,  shaking  at  intervals.  Add  50  c.c.  of  3  per  cent,  nitric  acid  and 
filter  through  the  asbestos  filter  and  wash  with  50  or  60  c.c.  of  the  same 
acid.  Run  25  c.c.  of  the  ferrous  sulphate  solution  into  the  flask  from  the 
pipette  and  titrate  with  the  permanganate  solution  to  a  faint  pink.  Sub- 
tract the  number  of  cubic  centimetres  of  the  permanganate  solution 
obtained  from  the  value  of  the  25  c.c.  of  ferrous  sulphate  solution  in 
permanganate,  and  the  result  is  the  number  of  cubic  centimetres  of  the 
permanganate  corresponding  to  the  manganese  in  the  manganese  sulphate 
solution  used.  Divide  the  weight  of  the  manganese  in  the  manganese 
sulphate  used  by  the  number  of  cubic  centimetres  of  permanganate,  and 
the  result  is  the  value  of  one  c.c.  of  the  permanganate  solution  in  man- 
ganese. 

Example. — One  gramme  manganese  sulphate  solution  contains  0.003562 
gramme  manganese ;  2.0372  grammes  manganese  sulphate  solution  equal 
0.0072565  gramme  manganese;  25  c.c.  ferrous  sulphate  solution  equal  24.5 
c.c.  permanganate  solution;  2.0372  grammes  manganese  sulphate,  after  oxi- 
dation and  addition  of  25  c.c.  ferrous  sulphate  solution,  require  3.6  c.c. 
permanganate  solution  ;  24.5  c.c. — 3.6  c.c. =20.9  c.c. ;  0.0072565  divided 
by  20.9=0.0003472,  or  i  gramme  permanganate  equals  0.0003472  gramme 
manganese.  If,  then,  I  gramme  of  steel,  after  oxidation  and  addition  of 


RAPID  METHODS  FOR  MANGANESE.  I2/ 

25  c.c.  ferrous  sulphate  solution,  requires  6.2  c.c.  permanganate  solution 
to  give  the  pink  color,  24.5 — 6.2—18.3X0.0003472=0.006354  gramme,  or 
the  sample  contains  0.635  per  cent,  manganese. 


Notes  and  Precautions. 

The  delicacy  of  the  reaction  of  manganese  in  nitric  acid  solution  with 
sodium  bismuthate  is  extraordinary, — 0.000005  gramme  of  manganese  gave 
an  appreciable  color  in  50  c.c.  of  solution. 

When  the  proper  precautions  are  observed,  this  method  for  materials 
containing  small  amounts  of  manganese,  say  up  to  2  per  cent.,  is  more 
accurate  than  any  other  method,  volumetric  or  gravimetric,  that  I  have 
ever  used. 

As  will  be  seen  in  the  description  of  the  various  methods  of  solution, 
the  use  of  hydrochloric  acid  has  been  avoided,  because  the  presence  of  even 
traces  of  this  reagent  is  fatal  to  the  accuracy  of  the  method.  Where  it  is 
impossible  to  avoid  its  use,  and  its  presence  is  suspected  in  the  final  nitric 
acid  solution,  the  addition  of  a  drop  or  two  of  silver  nitrate  will  overcome 
the  difficulty,  but  the  filter  must  be  rejected  after  using  it  for  filtering  a 
solution  so  treated. 

Any  form  of  asbestos  filtering  tube  may  be  used  for  filtering  off  the 
bismuthate,  but  the  perforated  cone  with  bell  jar,  shown  in  Fig.  55,  is  the 
most  satisfactory,  because  it  has  the  largest  area  of  filtering  surface.  One 
filter  may  be  used  for  fifty  or  more  determinations,  and  the  time  occupied  in 
filtering  and  washing  one  determination  is  only  from  one  minute  and  a  half 
to  three  minutes.  The  filtrate  must  be  perfectly  clear,  for  the  least  particle 
of  bismuthate  carried  through  will  vitiate  the  result  by  reacting  with  the 
excess  of  ferrous  sulphate.  As  soon  as  the  filtration  and  washing  are 
completed,  the  ferrous  sulphate  should  be  added  and  the  excess  titrated 
with  the  permanganate  solution,  as  the  permanganic  acid  gradually  decom- 
poses on  standing,  and  the  warmer  the  solution  the  more  rapid  is  the 
decomposition.  At  a  temperature  of  5°  C.  the  solution  will  remain  unaltered 
for  several  hours,  but  at  40°  C.  fifteen  minutes  will  show  an  appreciable 
change.  The  larger  the  amount  of  manganese  the  more  rapid  the  change. 


1 28  ANAL  YSIS  OF  IRON  AND  STEEL. 

It  is  especially  important  not  to  allow  the  solution  to  stand  after  adding  the 
ferrous  sulphate,  as  the  excess  of  this  reagent  reacts  with  the  nitric  acid  in 
a  few  minutes  and  the  formation  of  the  smallest  amount  of  nitrous  oxide  is 
fatal  to  the  accuracy  of  the  determination.  For  this  reason  it  is  important 
to  boil  off  every  trace  of  nitrous  oxide  when,  in  the  earlier  part  of  the 
operation,  sulphurous  acid  or  other  deoxidizing  agent  is  added. 

When  working  with  steels  of  unknown  manganese  content,  it  may  often 
happen  that  25  c.c.  of  ferrous  sulphate  solution  are  insufficient  to  entirely 
reduce  the  permanganic  acid,  in  which  case  an  additional  amount  of 
ferrous  sulphate  must  be  added,  and  the  pipette  shown  in  Fig.  56  has  been 
arranged  to  meet  this  contingency.  It  will  be  noticed  that  the  solution  of 
permanganic  acid  upon  the  addition  of  an  insufficient  amount  of  ferrous 
sulphate  does  not  necessarily  retain  its  pink  or  purple  color,  but  usually 
changes  to  a  dirty  brown.  When  this  occurs,  the  lower  part  of  the  pipette 
may  be  emptied  directly  into  the  flask  and  the  value  of  the  two  parts  taken 
as  the  amount  from  which  the  number  of  cubic  centimetres  of  permanga- 
nate, corresponding  to  the  excess  of  ferrous  sulphate,  must  be  subtracted. 
When  the  sample  is  low  in  manganese,  the  10  c.c.  portion  of  the  pipette 
alone  may  be  used,  so  that  the  arrangement  allows  a  great  deal  of  variation 
in  the  manganese  content  of  the  samples  worked  on. 

There  is  no  advantage  in  using  permanganate  solutions  differing  in 
strength  from  the  one  given  above,  but  the  strength  of  the  ferrous  sulphate 
solution  may  be  changed  to  meet  special  cases. 

I  am  surprised  that  this  method  has  not  come  into  general  use,  for  it 
combines,  in  a  remarkable  degree,  extreme  accuracy  and  great  rapidity 
with  simplicity  and  ease  of  manipulation. 

Deshayss  Method. 

This  method  is  based  on  the  fact  that  manganese  nitrate  when  boiled 
with  excess  of  nitric  acid  and  lead  peroxide  is  oxidized  to  permanganic 
acid,  which  is  reduced  again  by  a  standard  solution  of  sodium  arsenite. 

Dissolve  0.5  gramme  of  steel  or  pig-iron  in  30  c.c.  nitric  acid  (1.2  sp.gr.) 
and  boil  until  all  reactions  cease.  Add  cautiously  I  to  3  grammes  lead 
peroxide  or  red  lead  and  dilute  with  hot  water  to  about  60  c.c.  Heat  the 
solution  to  boiling  and  allow  the  lead  salt  to  settle.  Decant  the  solution 


RAPID  METHODS  FOR   MANGANESE.  129 

and  boil  the  residue  with  50  c.c.  of  nitric  acid  (1.13  sp  gr.).  Decant  as 
before  and  repeat  the  operation  until  the  supernatant  liquid  is  colorless. 
Filter  the  decanted  liquid  through  asbestos  and  titrate  with  a  standard 
solution  of  sodium  arsenite.  To  prepare  the  standard  solution,  dissolve 
4.96  grammes  of  arsenious  acid  together  with  25  grammes  of  sodium  car- 
bonate in  water  and  dilute  to  2500  c.c.  Dissolve  0.5  gramme  of  a  steel 
containing  a  known  amount  of  manganese  in  30  c.c.  nitric  acid  (1.2  sp.  gr.) 
and  treat  it  exactly  as  described  above  and  divide  the  percentage  of  man- 
ganese by  the  number  of  c.c.  of  the  standard  solution  required  to  decolorize 
the  permanganic  acid.  This  will  give  the  value  of  each  c  c.  of  the  standard 
solution  in  manganese.  For  steels  containing  over  0.5^  manganese  use 
0.25  gramme,  and  for  those  containing  over  i.ofo  use  only  o.i  gramme. 
Hot  solutions  of  nitric  acid  decompose  permanganic  acid  unless  the  per- 
manganic acid  is  very  dilute,  for  which  reason  it  is  necessary  to  use  decreas- 
ing amounts  of  the  steel  as  the  manganese  contents  increase. 

The  Color  Method  (for  Steel). 

This  method  was  first  suggested  by  Pichard,*  and  was  used  essentially 
in  its  present  form  by  Peters.f  It  requires  one  or  more  standard  steels  in 
which  the  manganese  has  been  most  carefully  determined  by  a  gravimetric 
method.  When  a  number  of  samples  are  to  be  tested  at  the  same  time,  as 
is  usually  the  case,  a  bath  like  the  one  shown  in  Fig.  86  is  necessary,  but 
for  the  manganese  color  method  it  should  contain  a  solution  of  calcium 
chloride,  which  boils  at  115°  C.  J  It  is,  of  course,  very  necessary  in  a 
method  of  this  kind  that  the  operations  should  always  be  conducted  as 
nearly  as  possible  under  the  same  conditions,  and  that  the  standard 
should  always  be  dissolved  at  the  same  time  as  the  samples  to  be  tested. 
Weigh  .2  gramme  of  each  sample  and  of  the  standard,  and  place 
them  in  8-inch  test-tubes  properly  numbered.  Pour  into  each  test-tube 
15  c.c.  nitric  acid  (1.2  sp.  gr.),  cover  each  with  a  small  glass  bulb  or  very 
small  funnel,  and  stand  the  test-tubes  in  the  holes  in  the  top  of  the 
bath,  as  shown  in  the  sketch,  Fig.  86.  Heat  in  the  bath  at  100°  C. 

*  Comptes-Rendus  Hebd.  des  Seances  de  1'Acad.  des  Sciences,  December  30,  1872. 
f  Chem.  News,  xxxiii.  35.  J  This  latter  modification  is  due  to  Mr.  S.  A.  Ford. 

9 


130  ANAL  YSIS  OF  IRON  AND  STEEL. 

until  solution  is  complete.  Pour  the  contents  of  a  test-tube  into  a  100  c.c. 
tube,  wash  out  the  test-tube  with  cold  water,  adding  it  to  the  solution  in 
the  100  c.c.  tube,  and  finally  dilute  to  the  100  c.c.  mark.  Mix  thoroughly 
by  placing  the  thumb  over  the  top  of  the  tube  and  turning  it  upside  down 
several  times.  Draw  out  10  c.c.  of  this  solution  with  a  pipette  graduated 
to  deliver  10  c.c.,  and  let  it  run  into  the  test-tube  in  which  the  solution  was 
made.  Treat  each  sample  in  this  way,  including  the  standard.  The  tube 
is  merely  washed  out  with  water,  but  the  pipette  can  best  be  cleaned  by 
drawing  it  full  from  the  100  c.c.  tube  of  the  fresh  sample,  throwing  the 
contents  away,  and  filling  it  a  second  time  to  deliver  into  the  test-tube. 
Stand  the  test-tubes  in  the  rack  again,  add  to  each  3  c.c.  nitric  acid  (1.2  sp. 
gr.),  replace  the  bulbs  or  funnels,  and  stand  the  rack  in  the  calcium  chloride 
bath,  the  solution  in  which  should  now  be  boiling.  When  the  solutions  in 
the  test-tubes  begin  to  boil,  add  to  each  .5  gramme  fine  lead  peroxide*  and 
boil  exactly  five  minutes.  The  lead  peroxide  can  readily  be  measured  by 
a  small  platinum  spoon,  made  to  hold  about  .5  gramme.  It  is  necessary 
that  the  solutions  in  the  test-tubes  should  boil,  and  it  is  easy  to  assure 
one's  self  of  this  fact  by  looking  down  into  the  test-tubes  after  the  action 
caused  by  the  addition  of  the  lead  peroxide  has  ceased.  Remove  the  rack 
from  the  bath  at  the  expiration  of  the  five  minutes,  and  stand  it  with  the 
test-tubes  in  cold  water,  to  cool  the  solutions  and  allow  the  insoluble  lead 
salt  to  settle.  The  insoluble  matter  settles  to  the  bottom  of  the  tube  in  a 
heavy  compact  mass,  leaving  the  supernatant  fluid  perfectly  clean.  When 
this  occurs,  which  is  usually  within  the  space  of  half  an  hour,  the  solutions 
are  ready  to  be  decanted  into  the  comparison-tubes. f  In  working  on  a 
number  of  steels  we  will  suppose  that  we  use  two  standards,  one  containing 
1.2  per  cent,  of  manganese,  the  other  0.6  per  cent.  As  we  weighed  out  .2 
gramme,  diluted  the  solution  to  100  c.c.,  and  took  10  c.c.  in  which  to  de- 
termine manganese,  the  amount  taken  corresponds  to  .02  gramme  of  the 
sample ;  and  if  we  dilute  the  solutions  of  the  standards  after  decanting  into 
the  comparison-tubes  to  24  c.c.,  I  c.c.  will  correspond  to  0.05  per  cent,  in 
the  high,  and  0.025  per  cent,  in  the  low,  standard.  Decant  each  solution  in 
turn  into  a  comparison-tube,  and  dilute  it  until  it  has  the  exact  tint  and 

*  See  page  57.  t  See  Fig.  85. 


RAPID   METHODS  FOR   MANGANESE.  131 

depth  of  color  of  the  standard  to  which  it  most  nearly  approximates  when 
first  decanted.  The  percentage  of  manganese  is  found  by  multiplying  the 
number  of  c.c.  to  which  the  sample  has  been  diluted  by  0.05  or  0.025, 
according  to  the  standard  with  which  it  has  been  compared.  If,  however, 
the  solution  of  a  sample  when  first  decanted  and  before  dilution  should  be 
lighter  in  color  than  the  lower  standard,  the  latter  may,  after  the  other 
samples  have  all  been  finished,  be  diluted  to  30  c.c.,  when  each  c.c.  will 
correspond  to  0.02  per  cent,  manganese,  or,  if  this  color  is  not  sufficiently 
light,  to  40  c.c.,  when  each  c  c.  will  correspond  to  0.015  per  cent,  manganese. 
When  even  this  color  is  not  sufficiently  light,  a  lower  standard  must  be 
used  for  comparison,  or  a  larger  amount  of  the  sample  taken  for  solution. 
The  comparison  of  the  colors  should  be  made  in  a  camera  or  box,  as 
shown  in  Fig.  89. 

The  direct  rays  of  the  sun  should  not  be  allowed  to  shine  on  the 
solutions,  and  a  northern  light  for  the  comparisons  is  preferable  to  any 
other. 

Walters 's  Modification. 

Taking  advantage  of  Dr.  Marshall's  suggestions  in  the  Chemical  News, 
vol.  Ixxxiii.  p.  76,  Mr.  Walters  has  elaborated  a  method  which  avoids  the 
necessity  for  filtration  and  for  the  use  of  a  calcium  chloride  bath  and  allows 
the  colors  of  the  solutions  to  be  compared  as  soon  as  they  are  cool.  It  is 
based  on  the  fact  that  when  a  solution  of  a  steel  in  nitric  acid  is  heated 
with  ammonium  persulphate  in  the  presence  of  a  small  amount  of  silver 
nitrate  the  manganese  is  oxidized  to  permanganic  acid.  Dissolve  .2 
gramme  of  the  sample  and  the  same  amount  of  a  standard  steel  in  test- 
tubes,  using  10  c.c.  of  nitric  acid  1.2  sp.  gr.  for  each.  Heat  in  water-bath 
until  solution  is  complete  and  all  nitrous  fumes  are  driven  off.  Add  to 
each  15  c.c.  of  a  solution  of  silver  nitrate  (1.33  grammes  to  I  litre),  equal  to 
.02  gramme  AgNO3.  Then  add  immediately  about  I  gramme  ammonium 
persulphate,  and  continue  heating  the  solution  for  about  half  a  minute 
after  the  oxidation  begins.  Place  the  tube  in  cold  water,  and  when  cold 
compare  as  usual. 

*  Harry  E.  Walters  in  Proceedings  of  Engineers'  Society  of  Western  Pennsylvania,  October, 
1901.  This  method  is  almost  universally  used  in  the  Pittsburg  district. 


132  ANALYSIS    OF  IRON  AND   STEEL. 

In  the  case  of  steels  containing  upward  of  0.75  per  cent,  manganese 
use  only  .1  gramme.  If  the  ammonium  persulphate  looks  very  dry,  it 
should  be  moistened  slightly  a  day  or  two  before  using;  10  c.c.  of  water 
to  a  pound  of  the  salt  is  sufficient. 

For  pig-iron  dissolve  I  gramme  in  a  small  beaker  in  30  c.c.  nitric  acid 
1.2  sp.  gr.  on  the  hot  plate.  Filter  into  a  100  c.c.  calibrated  flask  and 
dilute  to  the  mark.  Mix  well  and  pour  20  c.c.  (10  c.c.  if  high  in  manga- 
nese) into  a  test-tube,  warm,  and  add  a  little  ammonium  persulphate  to 
destroy  the  combined  carbon  and  give  a  clear  solution.  Add  5  c.c.  silver 
nitrate  solution  (i  gramme  of  the  salt  to  250  c.c.  water),  add  a  little  more 
ammonium  persulphate,  and  proceed  as  before. 


DETERMINATION    OF    CARBON. 

Carbon  differs  from  all  other  elements  in  iron  and  steel  in  that  it  is 
supposed  to  exist  in  several  conditions,  and  analytical  chemistry  supplies 
the  means  of  distinguishing  between  at  least  two  of  these  conditions. 
Until  within  a  few  years  it  was  considered  to  exist  in  two  forms,  as 
graphite  and  as  combined  carbon.  To  Karsten  is  due  the  recognition  of 
the  fact  that  graphite  is  a  form  of  pure  carbon,  and  not  a  compound  of 
carbon  and  hydrogen.  It  is  always  present  as  a  mechanical  mixture,  and 
is  thus  distinguished  from  the  other  form,  which  was  supposed  to  be 
combined  chemically  with  the  iron.  Of  late  years  the  opinion  has  been 
growing  that  "  combined  carbon"  exists  in  at  least  two  conditions  in  steel, 
but  as  yet  chemical  methods  for  separating  and  distinguishing  between 
these  conditions  have  failed,  so  far  as  quantitative  work  is  concerned. 
The  analytical  methods  here  given  are : 

The  Determination  of  Total  Carbon, 

The  Determination  of  Graphitic  Carbon,  and 

The  Determination  of  Combined  Carbon. 

DETERMINATION  OF  TOTAL  CARBON. 

We  may  divide  the  methods  for  the  determination  of  total  carbon  in 
iron  and  steel  into  the  following  classes  : 


DETERMINATION  OF  TOTAL  CARBON.  133 

A.  The  direct  treatment  of  the  borings  or  drillings  without  previous 
separation  of  the  iron,  including : 

1.  Direct  combustion  in  a  current  of  oxygen. 

2.  Direct  combustion  in  a  Gooch  tubulated  crucible. 

3.  Combustion    with    lead    chromate    and    potassium    chlorate    (Reg- 
nault). 

4.  Combustion    with    cupric    oxide   in    a    current  of  oxygen    (Kuder- 
natsch). 

5.  Solution  and  oxidation  of  the  borings  in    sulphuric,  chromic,  and 
phosphoric    acids,    the    volume    of    the    carbonic    acid    being    measured 
(Wiborg,  modified). 

6.  Solution  and  oxidation   of  the  borings   as  in   5,  the  carbonic  acid 
being  weighed. 

B.  Removal  of  the  iron  by  volatilization,  and  subsequent  combustion 
of  the  carbon,  including: 

1.  Volatilization  in  a  current  of  chlorine  (Berzelius,  Wohler). 

2.  Volatilization  in  a  current  of  hydrochloric  acid  gas  (Deville). 

C.  Solution  of  the  iron,  and  combustion  or  weighing  of  the  residue, 
including: 

1.  Solution  in  potassium-cupric  chloride,  filtration,  and  combustion  of 
the  residue  in  oxygen  (Richter). ' 

(a)  Combustion  of  residue  with  sulphuric  and  chromic  acids. 

(b)  Modification  by  Job  and  Davies. 

(c)  The  Shimer  crucible  for  combustion  in  air  or  oxygen. 

2.  Solution  of  the  iron  in  cupric  sulphate,  filtration,  and  combustion 
of  the  residue  in  a  boat  in  a  current  of  oxygen  (Langley). 

3.  Solution  of  the  iron  in  cupric  sulphate,  and  oxidation  of  the  residue 
by  chromic  and  sulphuric  acids  (Ullgren). 


1 34  ANAL  YSIS  OF  IRON  AND  STEEL. 

A.  1.    Direct  Combustion  in  a  Current  of  Oxygen. 

The  thorough  combustion  of  steel  drillings  and  subsequent  complete 
oxidation  of  the  contained  carbon  is  merely  a  question  of  temperature.  At 
one  time  I  was  firmly  convinced  that  at  a  temperature  slightly  above  a 
dark  red,  platinum  was  permeable  by  carbon  monoxide  and  dioxide  and 
that  it  was,  therefore,  dangerous  to  heat  a  platinum  tube  above  this  point  in 
the  determination  of  carbon.  Exhaustive  experiments  have  convinced  me 
of  the  fallacy  of  this  assumption.  With  the  proper  temperature,  any  ordi- 
nary drillings  may  be  completely  burned,  and  it  is  unnecessary  to  have  the 
steel  in  any  finer  state  of  subdivision  than  is  requisite  for  obtaining  a  proper 
average  of  the  sample.  These  results  apply  not  only  to  ordinary  steels  and 
pig  iron,  but  experiments  have  shown  conclusively  that  with  chrome-tung- 
sten steels  the  direct  method  is  the  only  one  capable  of  giving  accurate 
results,  those  obtained  by  solution  in  potassium-cupric  chloride  being 
invariably  from  iofi  to  40^  too  low. 

FIG.  57. 


Fig.  57  shows  the  boat  and  cover  used  in  this  method.  The  boat  is  6 
inches  (150  mm.)  long,  ^  inch  (9  mm.)  high,  and  y2  inch  (12  mm.)  wide  on 
top  and  slightly  narrower  on  the  bottom.  The  cover  fits  loosely  on  the 
boat,  and  is  provided  with  several  openings  formed  by  making  semicircular 
cuts  at  intervals  and  slightly  raising  the  edges.  The  openings  serve  to 
admit  the  oxygen  freely,  while  the  cover  prevents  the  particles  of  oxide  of 
iron  thrown  ofT  from  the  steel  during  the  combustion  from  reaching  the 
inside  of  the  tube. 


DETERMINATION  OF  TOTAL  CARBON. 


135 


Fill  the  boat  with  ignited  alumina  and  make  a  V-- 
shaped depression  in  the  middle  with  a  spatula,  pressing 
the  material  against  the  sides  of  the  boat.  Adjust  the 
cover  and  ignite  the  boat  and  its  contents  strongly,  to 
expel  any  carbon  dioxide  present  and  to  oxidize  any 
carbonaceous  matter  that  the  alumina  may  contain. 

Weigh  a  factor  weight  (2.7273  grammes)  of  the 
drillings  and  transfer  it  to  the  boat,  being  careful  to 
distribute  the  material  evenly  in  the  depression  with- 
out allowing  any  of  the  particles  to  be  in  contact  with 
the  platinum. 

The  general  arrangement  of  the  combustion  appa- 
ratus is  shown  in  Fig.  58.  It  consists  of  a  platinum 
tube,  B,  24  inches  (600  mm.)  long  and  ^j  inch  (16 
mm.)  in  diameter  from  the  joint  P  to  the  forward  end 
of  the  furnace  A,  where  it  is  contracted  for  a  length 
of  6  inches  (150  mm.)  to  a  diameter  of  ^  inch  (6 
mm.).  The  rear  end  has  a  ground  joint  P,  which  is 
made  perfectly  air  tight.  The  details  of  the  joint  are 
shown  in  Fig.  59. 

The  tube  has  a  strengthening  band  of  German  sil- 
ver, and  the  plug  through 
which  a  platinum  tube  4 
inches  (100  mm.)  long  and 
%  inch  (6  mm.)  in  diame- 
ter passes  is  made  of  phos- 
phor-bronze. The  forward 
end  inside  the  furnace  con- 
tains a  plug  of  loosely  wound  platinum  gauze  5^ 
inches  (138  mm.)  long,  completely  filling  the  bore  of 
the  tube,  and  a  similar  roll  2  inches  (50  mm.)  long 
fitted  with  a  loop  is  pushed  in  after  the  boat.  The 
rear  end  of  the  tube  at  the  joint  may  be  supported  by 
a  wire  from  above  or  by  a  stand  as  shown  in  the 


FIG.  58. 


FIG.  59. 


ANAL  YSIS  OF  IRON  AND   STEEL. 


sketch,  Fig.  58.  The  small  U-tube  C  is  filled  with  glass  beads  moistened 
with  chromic  acid  solution,  with  a  loose  plug  of  glass  wool  in  the  forward 
end.  This  serves  to  oxidize  any  sulphurous  anhydride  and  to  absorb  the 
sulphuric  anhydride  formed  from  the  sulphur  in  the  steel  during  the  com- 
bustion. This  tube  is  washed  out  daily  and  fresh  glass  wool  inserted. 
The  U-tube  D  contains  pieces  of  anhydrous  cupric  sulphate,  and  E, 
dried  granulated  calcium  chloride.  The  purifying  apparatus  for  oxygen  and 
air  is  shown  in  Fig.  60. 

FIG.  60. 


Oxygen  from  the  large  cylinder  is  passed  into  the  smaller  one  until  the 
pressure  is  from  150  to  200  pounds  to  the  square  inch,  when  the  larger 
cylinder  is  closed  and  the  gas  is  passed  from  the  smaller  cylinder  through 
the  apparatus,  it  having  been  found  difficult  to  regulate  the  flow  of  gas  prop- 
erly by  means  of  the  valve  in  the  large  cylinder  which  is  adapted  to  the 
heavy  pressure  of  gas  contained  in  these  cylinders.  While  filling  the 
smaller  cylinder  the  stopcock  K  is  closed,  and  when  the  valves  in  both 
cylinders  are  shut  the  pressure  is  relieved  by  opening  this  stopcock  after 
disconnecting  the  rubber  joint  J.  The  preheating  tube  I  is  of  platinum 
with  glass  fused  on  each  end  and  contains  fine  platinum  wire  in  the  loop. 
It  serves  to  burn  any  hydrocarbon  that  the  oxygen  may  contain.  The 
tubes  L  and  L'  and  M  and  M'  contain  potassium  hydrate  (1.27  sp.  gr.). 
The  U-tubes  N  and  N'  contain  fused  potassium  hydroxide.  The  oxygen 


DETERMINATION  OF  TOTAL  CARBON.  137 

passes  through  the  tubes  L,  M,  and  N  and  the  stopcock  S,  the  air  through 
L',  M',  and  N'  and  the  stopcock  S'.  A  Y-tube  connects  the  two,  and  the 
gas  or  air  passes  through  the  glass  tubes  connected  by  rubber  joints  into  the 
combustion-tube. 

The  absorption  apparatus  consists  of  the  Liebig  bulb  F  and  the  drying 
tube  G,  Fig.  58.  F  contains  solution  of  potassium  hydrate  (1.27  sp.  gr.). 
It  is  filled  by  attaching  a  short  piece  of  rubber  tubing  to  one  end  and  apply- 
ing suction  to  it,  the  other  end  being  immersed  in  the  potassium  hydrate 
solution  contained  in  a  beaker  or  dish.  The  end  must  be  wiped  dry  with 
a  little  filter-paper  and  the  inside  of  the  tube  dried  in  the  same  way.  When 
filled,  the  bulb  should  contain  the  solution  as  shown  in  Fig.  61.  When 
attached  to  the  apparatus,  the  gas  passes  first  into  the  large  bulb,  and,  the 
bulbs  being  inclined,  the  gas  bubbles  through  the  solution  in  the  three  bot- 
tom bulbs.  It  is  fitted  with  a  loop  of  platinum  wire,  as  shown  in  Fig.  61. 
The  drying  tube  contains  dried  calcium  chloride. 
The  small  bulb  of  the  drying  tube,  Fig.  62,  contains  FlG-  6l- 

a  plug  of  cotton-wool,  and  another  plug  of  the 
same  material  is  inserted  after  the  calcium  chloride. 
H  is  a  safety-guard  tube,  to  prevent  moisture  from 
getting  into  the  tube  G  during  the  combustion. 
The  short  rubber  tube  V  is  used  to  draw  a  little  air 
through  to  test  the  tightness  of  the  joints.  All  the 
stoppers  in  the  various  U  tubes  and  drying  tubes 
are  of  rubber.  A  copper  rod  is  used  to  introduce 
the  boats,  etc.,  into  the  tube  B.  When  not  at- 
tached to  the  apparatus,  the  ends  of  the  potash- 
bulb  F  and  drying  tube  G  are  closed  by  little  caps  of  rubber  tubing  (Fig. 
61)  made  like  the  tips  for  "  policemen."  When  on  the  balance,  however, 
they  should  be  closed  with  short  pieces  of  rubber  tubing  containing  bits  of 
capillary  glass  tubing,  as  shown  in  Fig.  62.  The  forward  end  of  the  drying 
tube  is  closed  in  the  same  way.  These  openings  are  too  small  to  allow  the 
condition  of  the  atmosphere  to  affect  the  weight  of  the  bulbs  by  loss  or 
gain  of  moisture,  but  they  serve  to  equalize  the  pressure  and  make  it  unnec- 
essary to  reopen  the  balance  case  until  the  bulbs  are  weighed. 


138 


ANAL  YSIS  OF  IRON  AND  STEEL. 


FlG.   62. 


It  is  very  necessary  in  filling  the  potash-bulb  to  avoid  getting  any  of  the 
solution  on  the  outside  of  the  bulb,  and  it  is  well  to  see  that  both  the  bulb- 
tube  and  the  drying  tube  are  perfectly  clean.  Wipe  the  potash-bulb  and 
drying  tube  with  a  piece  of  linen,  not  silk  (a  clean  linen  handkerchief  that 

does  not  leave  lint  on  the  glass  is 
very  good  for  this  purpose),  and 
place  them  on  the  balance. 

The  little  wire  stand  shown  in 
Fig.  62  is  very  convenient  for  hold- 
ing the  absorption  apparatus  in  the 
balance,  as  it  brings  all  the  weight 
on  the  pan,  instead  of  putting  the 
greater  part  on  the  beam  alone,  as 
is  the  case  when  the  potash-bulbs 
are  suspended  from  the  hook  on  the 
end  of  the  beam.  Allow  it  to  re- 
main about  thirty  minutes  to  get 
the  exact  temperature  of  the  bal- 
ance, and  weigh. 

In  the  mean  time  turn  on  the  oxygen  after  closing  the  stopcock  S',  Fig.  58, 
heat  the  platinum  tube  to  bright  redness  in  the  furnace,  and,  by  means  of  a 
small  blast- lamp  or  Bunsen  burner,  heat  the  forward  end  to  drive  out  any  sul- 
phuric acid  that  may  remain  in  the  tube.  Turn  out  the 
burners  of  the  »furnace,  turn  off  the  oxygen,  close  the  stop- 
cock S,  open  S'  and  start  a  slow  current  of  air  through 
the  apparatus.  When  the  tube  is  cool,  attach  the  U-tubes 
C,  D,  and  E,  shut  off  the  air,  close  the  stopcock  S',  and 
test  the  tightness  of  the  connections  by  attaching  a  flask 
or  bottle  containing  water  and  fitted  with  a  cork  carrying 
two  glass  tubes  as  shown  in  Fig.  63  to  the  forward  end 
of  E. 

By  drawing  air  through  the  tube  B  the  water  will  rise 
in  A,  and  if  it  keeps  its  level  for  a  few  minutes,  we  may  be  certain  that  all 
the  connections  are  air  tight.     If  it  does  not,  the  defective  connection  must 


FIG.  63. 


DETERMINATION  OF  TOTAL   CARBON.  139 

be  discovered  and  repaired.  Open  the  rear  end  of  the  tube,  insert  the  boat 
containing  the  drillings,  and  push  it  forward  by  means  of  a  rod  until  it 
is  in  contact  with  the  gauze  plug.  Push  the  short  gauze  plug  in  after  it, 
close  the  tube,  and  attach  the  weighed  absorption  apparatus  as  shown  in 
the  sketch,  Fig.  58.  Start  a  slow  current  of  oxygen  through  the  apparatus 
and  light  the  burner  under  the  preheater  and  the  first  three  or  four  burners 
under  the  forward  end  of  the  tube,  and  when  the  tube  is  red  hot  light  the 
other  burners  in  succession.  As  soon  as  the  forward  end  of  the  boat  gets 
hot  the  drillings  begin  to  burn  and  the  absorption  of  oxygen  is  very  rapid. 
The  valve  controlling  the  supply  of  oxygen  must  be  regulated  so  as  to  keep 
a  slow  current  of  gas  passing  through  the  absorption  apparatus.  It  is  not 
desirable  to  light  the  burners  in  very  rapid  succession,  as  under  these  cir- 
cumstances the  drillings  burn  very  rapidly,  and  the  heat  generated  by  the 
combustion  is  so  great  that  the  oxide  of  iron  melts,  and,  running  through 
the  alumina,  fuses  to  the  bottom  of  the  boat,  from  which  it  is  sometimes  dif- 
ficult to  dislodge  it.  It  may  even  in  extreme  cases  run  through  the  boat 
and  pass  to  the  tube  itself.  When  all  the  burners  are  lighted  and  the 
absorption  of  oxygen  has  practically  ceased,  turn  the  burners  up  to  the  full 
extent  and  maintain  the  tube  at  the  highest  possible  temperature  for  five 
minutes.  Turn  off  the  oxygen,  turn  on  the  air,  extinguish  the  burners,  and 
allow  the  air  to  pass  for  twenty  or  twenty-five  minutes.  Shut  off  the  air, 
detach  the  absorption  apparatus,  and  weigh  it  with  the  same  precautions  as 
before.  The  increase  in  weight  is  the  carbonic  acid  from  the  carbon  in  the 
steel  and  contains  27.27%  of  carbon.  When  the  factor  weight  is  used  for 
the  combustion,  each  tenth  of  a  milligramme  increase  of  weight  in  the 
absorption  apparatus  is  o.ooi  %  carbon  in  the  steel. 

2.    Direct  Combustion  in  a  Gooch  Tubulated  Crucible. 

Several  modifications  of  the  Shimer  crucible  have  been  proposed  for  the 
determination  of  carbon  in  steel  and  iron  and  most  of  them  are  available  for 
direct  combustion.  A  water-cooled  rubber  joint  has  its  disadvantages, 
which  are  not  found  in  the  Gooch  tubulated  crucible,  the  details  of  which 
are  shown  in  Fig.  100.  The  crucible  used  for  the  direct  combustion  of  steel 
and  iron  differs  in  some  of  its  details  from  the  one  shown  in  Fig.  100.  The 


140 


ANAL  YSIS  OF  IRON  AND  STEEL. 


flange  is  deeper,  the  cap,  while  the  conical  part  goes  to  the  bottom  of  the 
flange,  does  not  fit  tightly,  and  the  horizontal  tube  through  which  the  pro- 
ducts of  combustion  pass  is  much  longer  and  widens  out  at  the  point  C, 
Fig.  64,  for  a  distance  of  an  inch  (25  mm.).  This  portion  of  the  tube  is  filled 
with  fine  platinum  wire  and  heated  by  a  burner  to  facilitate  the  oxidation  of 
any  sulphur  dioxide  or  carbon  monoxide  that  may  be  present. 

FIG.  64. 


As  shown  in  the  cut,  Fig.  64,  the  apparatus  consists  of  the  crucible  A, 
which  is  supported  by  a  disk  of  asbestos  board,  F,  cut  to  fit  closely  under 
the  flange,  resting  on  the  ring  H,  attached  to  the  upright  of  the  stand  I.  A 
second  disk  of  asbestos  board,  G,  occupies  the  position  shown  in  the  cut  and 
is  held  in  place  by  a  piece  of  platinum  wire  encircling  the  crucible  under  the 
disk,  which  is  heavy  enough  to  keep  its  position  and  support  the  weight  of 
the  asbestos.  This  disk  serves  to  prevent  the  heat  from  extending  upward 


DETERMINATION  OF  TOTAL  CARBON.  14! 

on  the  crucible  and  melting  the  sodium  tungstate  in  the  flanged  joint.  The 
pieces  of  glass  tubing  D  and  E  are  attached  to  the  platinum  by  melting  a 
little  "sealing  in  "  glass  on  the  ends  of  the  platinum  tube  and  then  fusing 
the  ordinary  soft  glass  tubing  to  it. 

The  tube  D  is  connected  with  the  oxygen  and  air,  and  E  to  the  tube  C 
in  the  sketch,  Fig.  58.  The  apparatus,  therefore,  takes  the  place  of  the 
platinum  tube.  Two  ordinary  crucibles,  about  I  y2  inches  (37  mm.)  high 
and  narrow  enough  to  slip  easily  into  the  flanged  crucible,  should  be 
provided. 

Put  enough  alumina  in  the  flanged  crucible  A  to  fill  it  to  the  depth  of 
about  y2  inch  (12  mm.)  and  fill  one  of  the  small  crucibles  full  of  the  same 
material.  With  a  pair  of  forceps  put  the  small  crucible  in  the  large  one  and 
press  it  down  well  into  the  alumina.  By  means  of  the  blast-lamp  J  heat  the 
crucible  to  bright  redness  to  destroy  any  carbonaceous  matter  and  to  drive 
off  any  carbonic  acid  that  may  be  in  the  alumina.  Cool,  remove  the  small 
crucible,  and  with  a  glass  rod  press  the  alumina  down  to  form  a  conical 
hole  extending  half-way  to  the  bottom  of  the  crucible.  Weigh  one  gramme 
of  the  steel  or  iron  drillings,  transfer  them  carefully  to  the  crucible,  so  that 
none  of  them  may  be  in  contact  with  the  sides  of  the  crucible,  which  should 
be  perfectly  covered  by  the  alumina.  Place  the  crucible  in  the  large  cruci- 
ble A  as  before,  put  the  cap  B  in  place  in  the  flanged  joint,  and  connect  the 
tube  D  with  the  tube  from  the  oxygen  and  air  supplies,  Fig.  58.  Fill  the 
joint  around  the  cap  with  small  pieces  of  sodium  tungstate,  prepared  by 
melting  ordinary  sodium  tungstate  in  a  platinum  dish  with  one-tenth  its 
weight  of  tungstic  acid,  and,  when  perfectly  fused,  running  it  over  the  bottom 
and  sides  of  the  dish  and  allowing  it  to  cool  in  a  thin  layer.  Fuse  the 
sodium  tungstate  in  the  joint  by  a  flame  from  the  blast-lamp  J,  at  the  same 
time  passing  a  rapid  current  of  oxygen  through  the  apparatus  to  prevent  the 
carbonic  acid  of  the  flame  from  entering  the  tubulated  crucible.  Allow  it 
to  cool  while  the  current  still  passes,  then  shut  off  the  current,  attach  the 
tubes  C,  D,  and  E,  Fig.  58,  and  test  the  tightness  of  the  joints  by  means  of 
the  bottle,  Fig.  63,  as  directed  in  the  previous  method  Attach  the  pre- 
viously weighed  absorption  apparatus,  light  the  burner  K,  Fig.  64,  and 
start  the  oxygen  through  the  apparatus.  Heat  the  crucible  A,  Fig.  64,  with 


142  ANALYSIS  OF  IRON  AND  STEEL. 

the  blast-lamp  J  in  the  position  shown  in  the  cut.  The  flame  of  the  lamp 
should  be  large  enough  to  surround  the  crucible  and  the  full  heat  may  be 
applied  at  once,  the  current  of  oxygen  being  so  regulated  as  to  keep  up  a 
constant  current  of  three  or  four  bubbles  a  second  through  the  Liebig  bulb 
F,  Fig.  58.  When  the  absorption  of  oxygen  has  ceased,  turn  off  the  oxy- 
gen, turn  on  the  air,  extinguish  the  blast-lamp  J  and  the  lamp  K,  and  after 
the  air  has  passed  for  fifteen  or  twenty  minutes  shut  it  off  and  detach  and 
weigh  the  absorption  apparatus.  Detach  the  tube  E,  melt  the  sodium 
tungstate  in  the  joint  with  the  blast-lamp,  and,  holding  the  horizontal  tube 
of  the  cap  with  a  piece  of  asbestos  board,  withdraw  the  cap  from  the  joint. 
Allow  the  edge  to  rest  on  the  ring  F,  remove  the  small  crucible,  and  replace 
it  with  another  crucible  containing  a  weighed  portion  of  drillings.  Replace 
the  cap  in  the  joint,  start  a  rapid  current  of  oxygen,  fuse  the  sodium  tung- 
state, while  fused  press  the  tap  down  into  the  joint,  allow  it  to  cool,  and 
proceed  with  the  combustion. 

By  weighing  the  absorption  apparatus  while  full  of  oxygen,  before  and 
after  combustion,  the  determinations  may  be  very  rapidly  made,  and,  while 
they  are  not  perfectly  accurate,  they  are  much  more  accurate  than  the  color 
method. 

Notes  and  Precautions. 

Pig  iron  should  be  mixed  with  an  equal  weight  of  low-carbon  steel  or 
electrolytic  iron,  as  noted  under  Ferro-chrome  analysis. 

The  alumina  used  in  the  boats  and  crucibles  is  very  light ;  it  should  not 
be  pressed  down  in  the  boat,  for  the  more  compact  it  is  the  greater  the  ten- 
dency of  the  oxide  of  iron  to  fuse  and  penetrate  to  the  bottom. 

The  burners  should  not  be  lighted  in  succession  more  rapidly  than 
needed  to  keep  up  the  absorption  of  the  oxygen,  for  the  heat  of  combustion 
is  so  great  that  the  oxides  fuse  very  readily.  A  little  experience  will  show 
the  rate  at  which  the  oxygen  should  be  admitted  and  the  burners  lighted. 
If  the  operation  has  been  properly  conducted  the  fused  or  sintered  oxides 
may  be  readily  removed. 

The  alumina  remaining  in  the  boat  or  crucible  should  be  broken  up  and 
the  boat  filled  with  ignited  alumina  and  prepared  for  the  next  combustion. 


DETERMINATION  OF  TOTAL  CARBON.  143 

The  drillings  should,  if  possible,  be  taken  with  a  diamond-pointed  drill 
used  with  very  slow  speed,  which  furnishes  drillings  of  the  best  size  and 
shape.  They  should  usually  be  ground  in  a  Wedgwood  mortar,  which 
mixes  them  thoroughly  and  breaks  up  the  larger  pieces.  Long  curls  may 
be  flattened  by  pounding  in  the  hardened  mortar,  Fig.  7,  and,  if  necessary, 
cut  into  small  pieces  with  the  shears. 

3.    Combustion  with  Lead  Chromate  and  Potassium  Chlorate. 

This  method  requires  the  sample  to  be  very  finely  powdered.  Take  a 
piece  of  combustion-tubing  about  32  inches  (800  mm.)  long,  y2  inch  (12 
mm.)  internal  diameter,  y1^  inch  (1.5  mm.)  thick  in  the  walls;  heat  it  in  the 
middle  by  means  of  a  blast-lamp  until  it  softens,  draw  the  ends  apart  slightly, 
and  then,  keeping  the  ends  parallel,  draw  it  out  as  shown  in  Fig.  65. 

Allow   it   to    cool,   scratch    it 

FIG.  65. 

in     the    middle    with    a    file,      g 
and     break     it.       This    gives 
two     tubes,    each     about     16 
inches  (400  mm.)  long.     Fuse 

the  large  ends  slightly  so  as  to  round  the  sharp  edges,  but  avoid 
contracting  the  tube.  Wash  the  tubes  thoroughly,  using  a  rod  with 
a  piece  of  dark-colored  silk  or  linen  on  the  end ;  then  if  any  lint 
remains  on  the  inside  of  the  tube  it  can  easily  be  seen.  Dry  the 
tubes  by  heating  them  carefully  and  drawing  air  through  them,  then 
fuse  the  small  ends  and  cork  the  large  ends  to  keep  out  the  dust. 
Weigh  carefully  from  i  to  3  grammes  (i  gramme  of  pig-iron,  spiegel, 
or  ferro-manganese,  3  grammes  of  steel)  of  the  sample,  and  grind  it 
thoroughly  in  a  small  mortar  with  15  times  its  weight  of  fused  and 
powdered  lead  chromate  and  i^  times  its  weight  of  fused  and 
powdered  potassium  chlorate  or  potassium  bichromate.  Potassium 
bichromate  is  to  be  preferred,  as  a  little  chlorine  is  sometimes  given 
off  by  potassium  chlorate  when  used  in  this  manner.  Place  the 
combustion-tube  in  a  stand,  as  shown  in  Fig.  66,  and  push  down 
into  the  end,  with  a  clean  glass  rod,  a  little  ignited  asbestos.  The  asbestos 


144 


ANAL  YSIS   OF  IRON  AND   STEEL. 


FIG.   66. 


should  not  be  tightly  packed,  as  it  will  prevent  the  air  from  passing  in 
freely  at  the  end  of  the  operation.  Place  a  small,  dry,  perfectly  clean  fun- 
nel in  the  end  of  the  tube,  and  pour  through  it  enough  of  the  pure  pow- 
dered lead  chromate  to  fill  the  tube  for 
about  one  inch  of  its  length.  Hold  the 
mortar  under  the  funnel  so  that  anything 
that  falls  from  it  may  go  into  the  mortar, 
and  charge  the  mixture  into  the  tube  by 
means  of  a  small  platinum  spatula.  Clean 
out  the  mortar  by  grinding  in  it  two  or  three 
successive  small  portions  of  lead  chromate, 
charging  each  into  the  tube  through  the 
funnel.  Remove  the  funnel,  cork  the  tube, 
and,  holding  it  in  a  horizontal  position  with 
the  tail  up,  tap  it  gently  to  get  a  clear  space 
for  the  passage  of  the  gas  from  one  end  of  the 

tube  to  the  other.  Place  the  tube  in  the  combustion-furnace,  remove  the 
cork,  and  insert  in  its  place  a  smooth  velvet  cork,  through  the  centre  of 
which  passes  one  end  of  a  Marchand  U-tube.  The  half  of  this  tube  nearest 
the  combustion-tube  contains  anhydrous  cupric  sulphate,*  and  the  other 
half  granulated  dried  calcium  chloride,  tlje  two  reagents  being  sepa- 
rated by  a  small  plug  of  fibrous  asbestos  loosely  packed.  Weigh, 
and  attach  the  absorption  apparatus  and  safety-tube.  Apply  suction 
at  the  end  of  the  rubber  tube  on  the  forward  end  of  the  safety-tube, 
and  draw  a  few  bubbles  of  air  through  the  potash-bulb.  Allow  the 
liquid  to  recede  gradually;  if  it  maintains  its  level  in  the  bulb  for  a 
few  minutes,  the  joints  of  the  apparatus  may  be  considered  tight,  but 
if  it  gradually  falls,  it  is  proof  that  there  is  a  leak,  and  the  joints 
must  all  be  tightened.  If,  after  pushing  the  cork  as  far  as  possible 
into  the  end  of  the  combustion-tube  and  binding  all  the  rubber 
connections,  another  trial  still  shows  a  leak,  a  fresh  cork  must  be 
substituted.  When  the  joints  are  all  tight,  light  the  burner  at  the 


*  See  page  53. 


DETERMINATION  OF   TOTAL    CARBON.  145 

forward  end  of  the  tube,  and  each  burner  successively  as  the  flow 
of  gas  slackens,  bringing  the  tube  over  each  burner  to  a  red  heat 
before  lighting  the  next  one.  Maintain  the  whole  length  of  the  tube 
up  to  the  asbestos  at  a  good  red  heat  until  the  flow  of  gas  entirely 
ceases.  Then  pass  a  piece  of  rubber  tubing  attached  to  a  purifying 
apparatus  well  over  the  tail  of  the  tube,  which  should  be  cool 
enough  to  be  handled,  break  the  point  of  the  tail  inside  the  tubing, 
lower  the  lights  a  little,  and,  by  means  of  the  aspirator-bottles,  force 
about  I  litre  of  air  through  the  apparatus.  It  will  now  appear  as  in 
Fig.  67.  Turn  out  the  lights,  and  detach  and  weigh  the  absorption 


FIG.  67. 


apparatus,  with  the  precautions  mentioned  on  page  138.  The  increase 
of  weight  will  be  the  carbonic  acid  due  to  the  carbon  in  the  sample. 
This  contains  27.27  per  cent,  carbon. 

4.  Combustion  "with  Cupric  Oxide  in  a  Current  of  Oxygen. 

Prepare  the  combustion-tube  as  directed  in  the  last  method,  and  pour 
on  the  asbestos  in  the  end  of  the  tube  enough  cupric  oxide  to  fill  the  tube 
to  the  height  of  about  an  inch  (25  mm.).  Mix  the  weighed  sample — from 
I  to  3  grammes  in  a  fine  state  of  division — with  at  least  twenty  times  its 
weight  of  finely  powdered  pure  cupric  oxide,  charge  it  into  the  tube  as 
directed  on  page  144,  rinse  out  the  mortar  with  a  little  more  of  the  same 
material,  and  finally  fill  the  tube  to  within  an  inch  (25  mm.)  of  the  end 
with  granulated  cupric  oxide.  Make  the  combustion  exactly  as  directed 


146  ANAL  YSIS  OF  IRON  AND  STEEL. 

in  the  last  method  (page   145).     If  the  combustion   is  to    be    made  in  a 

current  of  oxygen,  which  is  much  the  best  plan,  instead  of  drawing  the 

FIG  68.  combustion-tube  out  to  a  point  and  sealing 

^^  it,  it  may  be  drawn  out  straight,  as  shown 

in    Fig.    68.     In    this    case,    attach   to   the 

drawn-out  end  when  the  tube  is  in  the  furnace  a  purifying  apparatus  for 
oxygen  and  air,  as  shown  in  Fig.  71,  and  conduct  the  operation  as  directed 
on  page  145. 

5.  Solution  and  Oxidation  of  the  Borings  in  Sulphuric,  Chromic, 
and  Phosphoric  Acids,  the  Volume  of  the  Carbonic  Acid  being 
measured. 

The  method  given  below  for  the  determination  of  carbon  in  steel  is 
generally  used  in  the  steel  works  laboratories  in  the  eastern  part  of  France, 
and  I  am  indebted  for  the  details  to  Monsieur  H.  A.  Brustlein  of  Jacob 
Holtzer  et  Cie,  of  Unieux,  at  whose  works  and  at  those  of  the  Acieries  de 
la  Marine  at  Saint-Chamond  the  various  improvements  in  the  method,  first 
suggested  by  Wiborg,*  have  been  worked  out. 

The  solutions  employed  are : 

1.  A  saturated  solution  of  chemically  pure  cupric  sulphate. 

2.  An  aqueous  solution  of  chromic  acid  (i   gramme  chromic  acid  to  I 
c.c.  water). 

3.  A  mixture  of  sulphuric,  phosphoric,  and  chromic  acids  made  up  as 
follows : 

Solution  of  chromic  acid  (solution  No.  2) 35  c.c. 

Water 190    " 

Concentrated  sulphuric  acid 75°    " 

Phosphoric  acid  (1.4  sp.gr.) 340    " 

In  preparing  solution  No.  2,  add  a  few  c.c.  of  sulphuric  acid  and  heat 
to  boiling  to  destroy  any  organic  matter  that  may  be  present. 

In  preparing  solution  No.  3,  heat  it  to  boiling  also  for  the  same 
purpose. 

*  Stahl  und  Eisen,  1887,  p.  465. 


DETERMINATION  OF  TOTAL  CARBON.  147 

The  apparatus,  as  shown  in  the  sketch  (Fig.  69),  consists  01  a  round- 
bottom  flask,  A,  of  250  c.c.  capacity,  with  a  long  neck.  The  flask  is  closed 
with  a  rubber  stopper  with  two  holes,  in  one  of  which  is  fitted  the  glass 

FIG.  69. 


stopper  funnel  B  and  in  the  other  the  tube  C  enclosed  in  the  condenser  D, 
through  which  a  stream  of  water  runs  during  the  operation.  The  tube  C 
is  connected  with  one  tube,  E,  of  a  three-way  stopcock,  a,  from  which  the 


148  ANAL  YSIS  OF  IRON  AND  STEEL. 

second  tube,  F,  opens  into  the  air,  and  the  third,  G,  connects  with  the  tube 
H  of  the  three-way  stopcock  b.  The  second  tube,  J,  from  this  stopcock  is 
fused  to  the  burette  K,  which  is  enclosed  in  the  tube  L  containing  water. 
The  lower  end  of  the  burette  connects  with  a  tube,  M,  of  small  interior 
diameter,  which  serves  as  a  level  tube  and  is  in  the  form  of  a"T ;  it  is  con- 
nected with  the  mercury  reservoir  N,  which  is  raised  and  lowered  by  the 
arrangement  O.  The  third  tube  of  the  stopcock  b  connects  with  the  tube 
P  of  the  stopcock  c,  the  second  tube,  Q,  of  the  stopcock  c  connects  with 
the  manometer  R,  and  the  third  tube,  S,  with  the  pipette  T,  which  runs 
into  the  bottle  U.  The  tubes  of  the  stopcocks  b  and  c,  the  manometer 
tube  R,  the  level  tube  M,  and  the  tubes  of  the  pipette  T  are  capillaries. 
The  manometer  tube  R  contains  water,  and  serves  to  accurately  adjust  the 
levels  when  taking  the  reading  of  the  burette  K.  When  the  manometer  is 
shut  off  from  the  burette  the  approximate  level  is  ascertained  by  means  of 
the  level  tube  M.  The  tube  F  of  the  stopcock  a  is  used  only  in  excep- 
tional cases :  first,  when  the  evolution  of  gas  is  insufficient  to  carry  the 
mercury  far  enough  down  the  burette  K,  in  which  case  air  is  drawn 
through  it  into  the  burette;  and  secondly,  when  the  evolution  of  gas  is 
so  great  that  it  is  necessary  to  make  two  absorptions  in  the  pipette  T,  in 
which  case  the  residue  from  the  first  absorption  is  discharged  through  the 
tube  F.  The  pipette  T,  which  is  of  about  400  c.c.  capacity,  contains  a  solu- 
tion of  potassium  hydroxide  of  1.27  sp.  gr.  The  bottle  U  is  of  about  one 
litre  capacity.  The  water  in  the  containing  tube  L  serves  to  keep  the  gas 
in  the  burette  at  the  ordinary  temperature  of  the  laboratory.  It  should  be 
protected  from  the  heat  of  the  burner  and  flask  by  a  screen. 

The  operation  is  conducted  as  follows : 

Connect  the  pipette  T,  by  means  of  the  stopcocks  b  and  ct  with  the 
burette  K,  and,  by  lowering  the  mercury  reservoir,  fill  the  pipette  with  the 
potassium  hydroxide  solution,  close  the  stopcock  c,  fill  the  burette  K  with 
mercury,  and  close  the  stopcock  b.  Weigh  I  gramme  of  drillings  into  the 
flask  A,  attach  it  to  the  apparatus,  start  the  water  through  the  condenser 
D,  and  connect  the  flask  with  the  burette  K  by  means  of  the  stopcock  a. 
Pour  15  c.c.  of  the  cupric  sulphate  solution  No.  I  into  the  funnel  tube  B, 
and  let  it  flow  into  the  flask.  Allow  it  to  act  long  enough  to  form  a  super- 


DETERMINATION  OF  TOTAL   CARBON.  149 

ficial  deposit  of  copper  on  the  drillings  (one  or  two  minutes  is  sufficient), 
then  add,  through  the  funnel  tube,  15  c.c.  of  solution  No.  2  and  135  c.c.  of 
solution  No.  3.  Heat  the  solution  in  the  flask  and  raise  it  slowly  to  the 
boiling-point.  By  means  of  the  reservoir,  keep  the  mercury  in  the  burette 
and  in  the  tube  M  nearly  level.  The  water  condensed  in  the  tube  C  drops 
back  into  the  flask  and  keeps  the  liquid  of  the  same  density,  while  the 
properly  cooled  gases  pass  into  the  burette. 

Allow  the  flask  A  to  cool  for  about  five  minutes,  and  then  run  into  it, 
through  the  funnel  tube  B,  enough  water  to  fill  the  flask  and  the  tube  to 
the  stopcock  ay  thus  forcing  all  the  gas  into  the  burette.  Close  the  stop- 
cock a  and  connect  the  burette,  by  means  of  the  stopcocks  b  and  c,  with 
the  manometer  R,  adjust  the  levels  accurately,  and  take  the  reading  of  the 
burette.  Then  by  means  of  the  stopcock  c  connect  the  burette  with  the 
pipette  T,  and,  by  raising  and  lowering  the  reservoir  N,  pass  the  gas  several 
times  back  and  forth  to  cause  the  potassium  hydroxide  to  absorb  all  the 
carbon  dioxide.  Finally  connect  the  burette  with  the  manometer  tube  R, 
adjust  the  levels,  and  take  the  reading  of  the  burette. 

The  burette  K  should  contain  a  few  drops  of  water  to  insure  the 
saturation  of  the  gases  with  aqueous  vapor.  The  difference  between  the 
two  readings  is  the  volume  of  the  carbon  dioxide.  Observe  the  readings 
of  the  thermometer  and  barometer,  and  reduce  the  volume  of  the  carbon 
dioxide  to  that  which  it  would  occupy  in  the  dry  state  at  o°  C.  and  760 
mm.  pressure.  (Table  V.) 

Multiply  the  volume  of  the  gas  so  obtained  by  0.0019663,  and  the 
result  is  the  weight  of  the  carbon  dioxide  in  grammes. 

6.  Solution  and  Oxidation  of  the  Borings  as  in  5,  the  Carbonic 
Acid  being-  weighed. 

Fig.  70  shows  the  details  of  the  apparatus  for  carrying  out  this  method. 
M  is  the  U-tube  for  purifying  the  air.  It  contains  fused  caustic  potash. 
A  is  the  flask  for  oxidizing  and  dissolving  the  sample.  The  piece  of  glass 
tubing  N  bent  at  a  right  angle  is  drawn  out  slightly  at  the  lower  end,  over 
which  a  piece  of  soft  gum  tubing  is  fitted,  forming  a  stopper,  which  fits 
tightly  in  the  top  of  the  bulb-tube  when  air  is  forced  through  the 


150 


ANAL  YSIS  OF  IRON  AND  STEEL. 


DE  TERM  IN  A  TION  OF  TO  TAL  CARBON.  1 5  I 

apparatus.  B  is  a  bulb-tube  for  introducing  the  reagents.  The  lower  end 
is  drawn  out  so  that  the  orifice  is  quite  small.  O  is  a  condenser,  P 
contains  anhydrous  cupric  sulphate,  Q  granular  calcium  chloride,  and  the 
small  bulb  of  P  and  Q  contains  cotton-wool.  The  Liebig  bulb  and  the 
tube  R  form  the  absorption  apparatus,  and  S  the  safety-tube.  Conduct 
the  operation  as  described  on  page  148,  pass  two  litres  of  air  through  and 
weigh  the  absorption  apparatus  as  described  on  page  138. 


B.  1.  Volatilization  of  the  Iron  in  a  Current  of  Chlorine,  and 
Subsequent  Combustion  of  the  Carbon. 

Spread  out  evenly  I  gramme  of  pig-iron  or  3  grammes  of  steel  on  the 
bottom  of  a  porcelain  boat  about  3  inches  (75  mm.)  long,  and  treat  it 
exactly  as  described  on  page  73  et  seq.  The  boat  when  withdrawn  from 
the  tube  contains  the  carbon,  slag,  and  oxides,  and  nearly  all  of  the  non- 
volatile chlorides,  such  as  manganous  chloride.  When  the  sample  con- 
tains much  manganese,  it  is  necessary  to  treat  the  residue  in  the  boat  with 
cold  water,  filter  it  on  a  small  plug  of  ignited  asbestos,  return  it  to  the  boat, 
and  dry  it  before  burning  it  off  As  this  adds  very  considerably  to  the 
time  required  for  the  determination,  it  is  best  to  adopt  some  other  method 
for  the  determination  of  carbon  in  such  materials  as  spiegel  and  ferro- 
manganese.  Introduce  the  boat  into  the  tube  B  of  the  apparatus  Fig.  71. 
This  apparatus  consists  of  a  ten-burner  combustion-furnace  A,  through 
which  runs  the  porcelain  tube  B.  This  tube  is  about  25  inches  (625  mm.) 
long  and  ^  inch  (18  mm.)  internal  diameter.  It  projects  6  inches  (150  mm.) 
outside  the  furnace  at  each  end,  and  the  sheet-iron  screens  L  prevent  the 
heat  from  reaching  the  stoppers  P  and  S.  The  tube  is  filled  for  a  length 
of  6  inches  (150  mm.),  or  from  about  the  middle  of  the  tube  to  the  forward 
end  of  the  furnace,  with  copper  dioxide,  which  is  best  made  by  rolling  up 
tightly  a  piece  of  coarse  copper  gauze  6  inches  (150  mm.)  long  until  it 
makes  a  roll  nearly  filling  the  bore  of  the  tube,  and  heating  it  for  an  hour 
in  a  current  of  oxygen.  A  piece  of  thin  sheet-silver  4  inches  long,  and 
forming  a  roll  completely  filling  the  bore  of  the  tube,  is  placed  just  in  front 
of  the  copper  dioxide :  it  serves  to  absorb  any  chlorine  given  off  during 


152 


ANAL  YSIS  OF  IRON  AND  STEEL. 


I 


DETERMINATION  OF  TOTAL   CARBON.  153 

the  combustion.*  A  roll  of  copper  gauze  two  inches  long,  with  a  loop  in 
one  end,  thoroughly  oxidized,  is  pushed  in  after  the  boat  containing  the 
carbon.  The  cylinder  O  contains  oxygen  under  pressure.  The  bottles 
F,  F  serve  to  force  air  through  the  apparatus  to  replace  the  oxygen  at  the 
end  of  the  operation.  The  stopcock  T  serves  to  regulate  the  flow  of  water, 
and  consequently  of  air.  When  all  the  water  has  run  from  the  upper  into 
the  lower  bottle,  it  is  siphoned  out  of  the  latter  and  returned  to  the  former. 

The  purifying  apparatus  M  and  N,  for  oxygen  and  air  respectively,  con- 
sist of  Liebig  potash-bulbs  filled  with  solution  of  potassium  hydrate  (1.27 
sp.  gr.),  and  U-tubes,  the  sides  next  the  potash-bulbs  filled  with  dry  pumice 
and  the  other  sides  with  calcium  chloride.  The  glass  stopcocks  Q  and  R 
shut  off  the  purifying  apparatus  on  their  respective  sides  when  the  oxygen 
or  air  is  passing  through  the  other  set.  The  T-tube  D  connects  the  two 
sets  of  apparatus,  the  third  limb  passing  through  the  glass  in  the  side  of 
the  hood,  and  connecting  by  means  of  the  bent  glass  tubes  with  the  rubber 
stopper  P,  which  fits  in  the  porcelain  tube  B.  All  the  connections  are 
made  with  glass  tubes  joined  together  by  rubber  tubing,  the  ends  of 
the  glass  tubing  being  brought  close  together  inside  the  rubber.  This 
is  to  avoid  carrying  the  oxygen  or  air  through  rubber  tubing,  which  gives 
off  volatile  hydrocarbons.  The  Marchand  U-tube  G  contains  anhydrous 
cupric  sulphate  to  absorb  any  hydrochloric  acid  which  may  be  evolved 
during  the  combustion.  It  is  joined  to  the  tube  B  by  a  rubber  stopper. 
The  U-tube  H  contains  granulated  dried  calcium  chloride.f  The  absorp- 
tion apparatus  is  that  described  on  page  137. 

The  form  of  absorption  apparatus  here  figured  is  only  one  of  many 
that  may  be  used  for  this  purpose.  It  has  the  advantage  of  simplicity  and 
it  can  be  easily  wiped  clean  from  any  moisture  that  it  may  get  by 
handling,  from  dust  or  from  gases  of  the  laboratory.  The  arrange- 
ment shown  in  I,  Fig.  84,  page  172,  is  also  very  convenient.  It  stands 
on  the  pan  of  the  balance,  and,  when  once  put  together  and  wiped  clean, 


*  This  roll  of  silver  must  occasionally  be  removed  and  ignited   in  a   current  of  hydrogen  to 
remove  the  chlorine. 
t  See  page  52. 


1 54  ANAL  YSIS  OF  IRON  AND  STEEL, 

it  may  be  managed  so  that  the  hands  come  in  contact  with  it  as  little 
as  possible.  On  the  other  hand,  the  potash-bulb  is  rather  difficult  to  fill, 
and  the  drying  tube  is  necessarily  smaller  and  contains  less  calcium 
chloride,  so  that  a  very  rapid  current  of  air  or  oxygen  may  carry  mois- 
ture from  the  potash-bulb  through  it  on  account  of  the  smaller  surface  of 
the  drying  material.  Instead  of  a  potash-bulb  a  U-tube  containing  soda- 
lime  is  sometimes  used,  but  as  soda-lime  absorbs  carbonic  acid  only  on 
the  surface  of  the  particles,  it  is  not  so  certain  in  its  action  and  is  not  to  be 
recommended.  No  matter  what  form  of  apparatus  is  selected,  care  must 
be  used  to  fill  the  potash-bulb  frequently  with  fresh  potassium  hydrate  and 
the  drying  tube  with  dry  calcium  chloride. 

300  grammes  of  potassium  hydroxide  to  the  litre  of  water  give  a 
solution  of  1.27  sp.  gr. 

Place  the  absorption  apparatus  on  the  balance  and  allow  it  to 
remain  about  thirty  minutes  to  get  the  exact  temperature,  and  weigh. 
Attach  the  absorption  apparatus  as  shown  in  the  sketch,  Fig.  71, 
insert  the  boat  in  the  tube  by  means  of  the  rod  C,  pushing  it  up 
against  the  cupric  oxide,  insert  the  short  roll  of  oxidized  gauze  as 
far  as  the  inside  of  the  screen  L,  and  close  the  tube  with  the  stop- 
per P.  Shut  the  stopcocks  R  and  Q,  and,  by  applying  suction  at  V, 
draw  a  few  bubbles  through  the  potash-bulb  I.  When  the  liquid 
recedes  in  the  potash-bulb,  it  should  keep  its  level  for  a  few  minutes ; 
if  it  does  not,  there  is  a  leak  in  some  of  the  connections,  which 
must  be  discovered  and  stopped  before  proceeding  with  the  combus- 
tion. When  everything  is  tight,  open  R  and  start  a  slow  current  of 
oxygen  through  the  apparatus.  Light  the  two  forward  burners  of  the 
furnace,  turning  them  low  to  heat  the  oxidized  copper  gauze,  raise  the 
heat  gradually  until  the  tube  appears  red,  and  then  light  the  last 
burner  to  heat  the  short  roll  of  oxidized  copper  gauze.  As  soon  as 
this  end  of  the  tube  is  hot,  light  the  third  burner  from  the  forward 
end,  and  a  few  minutes  afterwards  the  fourth  burner,  which  is  directly 
under  the  forward  end  of  the  boat.  Light  each  burner  in  succession 
from  this  one  until  all  are  lighted  and  turned  high  enough  to  heat 
the  tube  red  hot.  Allow  them  to  burn  for  fifteen  minutes,  then  shut 


DETERMINATION  OF   TOTAL    CARBON.  155 

off  the  oxygen,  close  R,  open  Q,  and  by  means  of  the  stopcock  T 
start  a  current  of  air  through  the  apparatus.  By  means  of  the  gas- 
cock  X  lower  all  the  lights  of  the  furnace  together  very  slowly,  to 
avoid  cracking  the  tube,  and  finally  turn  them  out.  About  I  litre  of 
air  should  run  through  at  the  rate  of  three  bubbles  a  second;  this 
will  about  half  empty  the  upper  bottle  L.  Close  T  and  Q,  detach 
the  absorption  apparatus,  close  the  ends  of  I  and  J  with  the  little 
rubber  caps,  and,  after  wiping  the  bulb  and  tube  gently  with  the  linen 
handkerchief  to  remove  any  moisture  caused  by  the  handling,  place 
them  on  the  balance.  Weigh  with  the  same  precautions  as  before ; 
the  increase  in  weight  is  carbonic  acid,  which  contains  27.27  per  cent, 
carbon.  When  several  combustions  are  to  be  made  in  succession,  as 
soon  as  the  absorption  apparatus  is  detached  as  directed  above,  re- 
move the  boat  from  the  tube,  replace  it  with  another  containing  a 
second  sample,  attach  a  second  absorption  apparatus  which  has  just 
been  weighed,  and  proceed  with  the  combustion.  While  the  second 
combustion  is  in  progress,  the  first  absorption  apparatus  may  be  weighed, 
and  the  weight  then  obtained  can  be  used  for  the  first  weight  of  the 
absorption  apparatus  for  a  third  combustion.  Before  the  absorption 
apparatus  shall  have  increased  .5  gramme  in  weight  from  the  original 
weighing,  the  potash-bulb  must  be  emptied  and  refilled  with  a  fresh 
solution.  When  the  final  combustion  for  the  day  is  finished,  place  a 
piece  of  glass  rod  in  the  open  end  of  the  connection  of  H,  remove 
the  boat  from  the  tube  B,  replace  the  short  roll  of  oxidized  copper 
gauze  in  the  tube,  insert  the  stopper  P,  but  not  tightly,  open  R  and 
Q,  and  loosen  the  stopper  in  the  bottle  F.  Place  pieces  of  glass  rod 
in  the  ends  of  the  safety-tube  K,  to  prevent  access  of  moisture.  When- 
ever the  apparatus  has  been  out  of  use  for  a  day,  before  making  a  com- 
bustion or  set  of  combustions  remove  the  piece  of  glass  rod  from  the 
forward  end  of  the  U-tube  H,  insert  in  its  place  a  piece  of  glass  tubing 
drawn  out  at  the  forward  end  to  a  small  orifice,  start  a  current  of 
oxygen  through  the  apparatus,  light  the  burners  in  the  furnace,  raising 
the  heat  very  gradually,  keep  the  tube  at  a  red  heat  fifteen  minutes, 
turn  off  the  oxygen,  start  the  air,  lower  the  burners  gradually,  and 


156 


ANAL  YSIS   OF  IRON  AND   STEEL. 


pass  a  litre  of  air  through  the  apparatus.  It  will  then  be  ready  for 
the  combustion.  In  very  damp  weather  it  is  almost  impossible  to  get 
good  results,  the  condensation  of  moisture  on  the  absorption  apparatus 
rendering  the  weighing  extremely  difficult  even  when  the  utmost  care 
is  used. 

This  difficulty  may  be  overcome  almost  entirely  by  using  another 
absorption  apparatus  of  similar  form  as  a  counterpoise.  This  counterpoise 
should  be  arranged  to  weigh  2  or  3  grammes  less  than  the  absorption 
apparatus.  The  superficial  area  of  the  two  being  practically  equal,  the 
condensation  on  the  two  surfaces  is  the  same. 

The  calcium  chloride  in  the  drying-tube  of  the  absorption  apparatus 
must  frequently  be  renewed,  as  it  absorbs  the  moisture  carried  over  from 
the  caustic  potash,  and  the  success  of  the  operation  depends  upon  the 
oxygen  and  air  leaving  the  absorption  apparatus  in  the  same  hygroscopic 
condition  as  when  they  enter  it. 

2.  Volatilization  of  the  Iron  in  a  Current  of  Hydrochloric  Acid 
Gas,  and  Subsequent  Combustion  of  the  Carbon. 

The  process  is  exactly  the  same  in  this  method  as  in  that  just  described, 
a  current  of  hydrochloric  acid  gas  being  substituted  for  one  of  chlorine. 
The  apparatus  for  generating  this  gas  is  the  same  as  the  one  used  for 
chlorine,  common  rock-salt  in  pieces  about  as  large  as  a  filbert  being 
substituted  for  manganese  dioxide,  and  sulphuric  acid,  diluted  with  two- 
thirds  its  bulk  of  water,  for  hydrochloric  acid. 

C.  1.  Solution  in  Potassium-Cupric  Chloride,  Filtration,   and 

"Weighing-  or  Combustion  of  the  Residue. 

Place  I  gramme  of  pig-iron,  spiegel,  or  ferro-manganese  in  a  400  c.c. 
Griffin's  beaker,  and  add  100  c.c.  of  a  saturated  solution  of  potassium- 
cupric  chloride  and  7.5  c.c.  hydrochloric  acid.  For  steel  or  puddled  iron, 
use  3  grammes  and  add  200  c.c.  of  potassium-cupric  chloride  solution  and 
15  c.c.  strong  hydrochloric  acid.  Stir  the  solution  constantly  with  a  glass 
rod  for  some  minutes  at  the  ordinary  temperature.  The  more  it  is  stirred 
the  more  rapid  will  be  the  solution  of  the  iron  and  of  the  precipitated 


DETERMINATION  OF  TOTAL  CARBON. 


157 


copper.  The  beaker,  carefully  covered,  may  now  be  placed  on  the  top  of 
the  air-bath  or  on  a  cool  part  of  the  iron  plate,  but  the  solution  should 
never  be  heated  hotter  than  60°  or  70°  C.,  and  it  should  be  stirred  as  often 
as  practicable. 

As  the  most  tedious  part  of  the  determination  of  carbon  in  steel  is 
frequently  that  which  has  to  do  with  the  decomposition  of  the  steel  and 
the  solution  of  the  precipitated  copper,  particularly  in  the  case  of  low 
steels,  the  samples  being  nearly  always  in  lumps,  and  it  not  being  desirable 
to  separate  these  larger  particles  for  fear  that  the  fine  stuff  alone  may  not 
represent  a  true  average,  the  machine  shown  in  Fig.  72  is  very  useful. 


FIG.  72. 


.c 


0  ,.0 

D 


It  consists  of  a  framework,  A,  of  brass,  cast  in  one  piece  for  the  sake  of 
rigidity.  It  is  fastened  to  the  table  by  lugs  and  screws  not  shown  in  the 
cut.  The  shelf  on  which  the  beakers  stand  has  on  it  a  piece  of  asbestos 
board  with  holes  to  fit  exactly  the  bottoms  of  the  beakers  to  prevent  them 
from  moving.  To  further  increase  the  stability  of  the  beakers  (which 
should  be  of  very  heavy  glass)  their  bottoms  are  ground  on  a  glass  plate 
with  fine  emery  until  they  have  a  good  bearing  surface  all  around.* 

The  tops,  which  are  covered  when  on  the  machine  with  a  plate  of  glass, 
F,  ground  on  one  side  and  perforated  to  allow  the  passage  of  the  stirring- 
rods  E,  are  likewise  ground,  so  that  when  slightly  moistened  the  ground 


I58 


ANAL  YSIS   OF  IRON  AND   STEEL. 


FIG.  73. 


glass  prevents  almost  entirely  all  movement  of  the  covers  on  the  beakers 
when  the  machine  is  in  motion. 

The  small  wooden  pulleys  C  are  fitted  with  brass  spindles,  which  run 
through  the  upper  cross-piece  and  have  on  their  lower  ends  pieces  of 
rubber  tubing,  which  serve  to  hold  the  stirring-rods.  The  stirring-rods 
are  bent  as  shown  in  the  cut,  to  give  the  proper  motion  to  the  liquid.  A 
small  motor,  B,  adapted  to  the  strength  of  the  current,  furnishes  the 
requisite  power.  The  motor,  if  properly  -wound,  may  be  attached  to  an 
ordinary  incandescent  lighting  current,  but  a  sewing-machine  motor  run 
by  a  dipping  battery  of  three  bichromate  cells  is  sufficient  to  give  the 
necessary  number  of  revolutions. 

The  fact  that  it  is  not  only  unnecessary  to  use  a  neutral  solution,  but 
that  the  use  of  a  neutral  solution  gives  inaccurate  results,  seems  now  to 

be  thoroughly  established  by 
the  experiments  of  the  Amer- 
ican members  of  the  International 
Steel  Standards  Committee.  The 
best  practice  is  to  add  about  10 
per  cent,  of  hydrochloric  acid 
to  the  solution  of  the  potassium- 
cupric  chloride.  The  reactions 
occurring  may  be  considered  as 
Fe  +  CuCl2  =  FeCl2  +  Cu  and 
Cu  +  CuCla  =  2CuCl.  The  part 
taken  by  the  potassium  chloride 
does  not  seem  very  clear,  but 
the  fact  remains  that  the  pre- 
cipitated copper  is  much  more 
soluble  in  the  double  salt  than  in  any  other  menstruum.  When  the 
precipitated  copper  is  all,  or  very  nearly  all,  dissolved,  which  is  usually 
the  case  in  half  an  hour  after  the  solution  of  potassium-cupric  chloride 
is  added  to  the  drillings,  run  a  little  of  the  acidulated  double  chloride 
around  the  sides  of  the  beaker  by  means  of  the  rod,  wash  the  rod 
over  the  beaker  with  a  jet  of  water,  and  let  the  beaker  stand  for  a  few 


DETERMINATION  OF   TOTAL    CARBON.  159 

minutes  to  allow  the  carbonaceous  matter  to  settle.*  The  best  form 
of  filtering-apparatus  is  shown  in  the  annexed. sketches.  It  consists  of 
the  perforated  platinum  boat  (Fig.  73)>  which  fits  in  the  platinum  holder. 
To  prepare  the  boat  for  use,  place  it  in  the  holder,  as  shown  in  Fig.  74, 

FIG.   74. 


attach  the  pump,  but  do  not  start  it.  Fill  the  boat  with  prepared 
abestos  f  suspended  in  water,  pour  enough  around  the  outside  of  the 
boat  to  fill  the  space  a,  Fig.  74,  and  start  the  filter-pump.  Continue 
pouring  the  suspended  abestos  into  the  space  a,  Fig.  74,  until  enough 

*  Barba  suggests  adding  to  the  solution  ignited  asbestos  in  water  to  make  the  carbonaceous 
matter  settle  and  to  prevent  its  clogging  the  filter.  This  is  a  most  admirable  suggestion  and  should 
be  generally  adopted. 

f  See  page  27. 


l6o  ANALYSIS   OF  IRON  AND   STEEL. 

is  drawn  into  the  joint  to  make  a  good  packing.  By  pressing  it  in  all 
round  with  a  spatula  the  joint  may  be  made  very  tight.  Pour  enough 
of  the  suspended  asbestos  into  the  boat  to  make  a  good,  thick  felt,  and 
press  it  down  firmly  all  over  the  bottom  of  the  boat  with  something  like 
the  square  end  of  a  lead-pencil,  to  make  it  compact.  Detach  the  pump, 
remove  the  boat  from  the  holder  carefully  so  as  to  leave  the  packing 
on  the  sides  of  the  holder,  and  move  it  up  with  the  end  of  a  spatula, 
so  that  it  will  remain  as  shown  in  Fig.  73.  Place  another  boat  in  the 
holder,  press  the  packing  into  the  joint  a,  Fig.  74,  with  the  end  of  a 
spatula,  fill  the  boat  with  suspended  asbestos,  and  start  the  pump. 
If  necessary,  pour  a  little  of  the  finer  suspended  asbestos  fibre  into  the 
joint  to  make  it  perfectly  tight,  and  prepare  the  felt  in  the  boat  as 
before.  Dry  the  boats,  and  ignite  them  in  the  combustion-tube,  two  at  a 
time,  in  a  current  of  oxygen.  Fit  one  of  these  prepared  boats  in  the 
holder,  press  the  packing  into  the  joint  as  before,  first  moistening  it 
slightly  if  it  has  become  dry,  start  the  pump,  and  pour  into  the  boat 
enough  suspended  asbestos,  which  has  been  ignited  in  oxygen,  to 
form  a  thin  film  on  the  top  of  the  felt.  This  film  will  hold  the  silica,  ferric 
phosphate,  etc.,  from  the  carbonaceous  residue,  and,  after  the  combustion, 
will  usually  turn  up  at  the  edges,  so  that  it  can  readily  be  detached  from 
the  main  felt,  leaving  the  boat  ready  for  another  filtration. 

The  boat  being  thus  prepared,  pour  into  it  the  solution  of  the  iron  or 
steel,  guiding  the  stream  by  a  small  glass  rod  held  against  the  tip  of  the 
beaker.  The  solution,  if  the  joint  a,  Fig.  74,  is  tight,  and  the  pump  works 
well,  will  usually  run  through  the  felt  as  rapidly  as  it  can  be  poured  into 
the  boat.  When  the  supernatant  fluid  has  all  run  through,  transfer  the 
carbonaceous  matter  to  the  boat  by  a  fine  stream  of  cold  water  from  a 
washing-flask.  Pour  into  the  beaker  about  10  c.c.  of  dilute  hydrochloric 
acid,  run  it  all  around  the  inside  of  the  beaker  by  means  of  the  rod  to 
dissolve  any  adhering  salt,  wash  the  glass  rod  and  wash  down  the  sides 
of  the  beaker  with  a  jet  of  water,  and  decant  the  acid  into  the  boat,  filling 
it  almost  up  to  the  edge.  Wash  the  carbonaceous  matter  in  the  boat 
thoroughly  with  hot  water  by  filling  the  boat  from  the  beaker  and  allow- 
ing it  to  suck  through  dry,  but  do  not  attempt  to  throw  a  jet  of  water  into 


DETERMINATION  OF   TOTAL    CARBON.  l6l 

the  boat  from  the  washing-flask,  as  it  will  be  almost  certain  to  throw  some 
of  the  carbonaceous  matter  from  the  boat  or  cause  it  to  crawl  over  the 
side.  In  decanting  the  water  from  the  beaker,  the  lip  must  not  be  allowed 
to  touch  the  surface  of  the  liquid  in  the  boat,  as  a  film  of  carbonaceous 
matter  will  run  up  the  inside  of  the  beaker.  Pour  a  little  dilute  acid  into 
the  joint  between  the  boat  and  holder,  allow  it  to  suck  through  the  pack- 
ing, and  wash  it  several  times  with  hot  water.  The  carbonaceous  matter 
from  pig-iron,  puddled  iron,  spiegel,  ferro-manganese,  and  ingot  steel 
usually  washes  like  sand,  but  that  from  steel  which  has  been  hardened, 
tempered,  hammered,  or  rolled  is  apt  to  be  more  or  less  gummy,  stopping 
the  filter  and  rendering  the  filtration  and  washing  prolonged  and  tedious. 
It  is  also  apt  to  adhere  more  or  less  to  the  sides  of  the  beaker,  and  must 
be  wiped  off  by  a  little  wad  of  ignited  fibrous  asbestos,  held  in  a  pair  of 
platinum-pointed  forceps  like  those  shown  in  Fig.  75. 

This  wad  is  then  placed  in  the  boat.  When  the  carbonaceous  matter 
is  thoroughly  washed  and  sucked  dry,  detach  the  pump,  remove  the  boat 
from  the  holder,  wipe  the  outside 
carefully  with  a  piece  of  silk,  place  it 
in  a  dish  covered  with  a  watch-glass, 
and  dry  it  in  a  water-bath  or  an  air- 
bath  at  100°  C.  When  dry,  insert  the  boat  in  the  tube  (Fig.  71),  and  burn 
off  the  carbon  as  directed  on  page  154.  Instead  of  the  porcelain  tube,  a 
platinum  tube  of  the  dimensions  shown  in  Fig.  58,  page  135,  may  be  used 
to  very  great  advantage.  The  U-tube  C  contains  water.  The  limb  of  the 
U-tube  D  nearest  the  platinum  tube  contains  anhydrous  cupric  sulphate  * 
and  the  forward  limb  anhydrous  cuprous  chloride. f  E  contains  dried,  not 
fused,  calcium  chloride,  and  in  the  bulb  next  to  G  is  a  small  wad  of  cotton- 
wool. The  object  of  the  cuprous  chloride  is  to  absorb  any  chlorine  that 
may  come  over  during  the  combustion.  If  any  should  come  over  it  would 
be  mixed  with  hydrochloric  acid  and  moisture,  and  all  then  would  be  ab- 
sorbed by  the  water  in  C  and  the  salts  in  the  tube  D.  The  burners  in  the 
furnace  should  be  lighted  in  the  order  directed  on  page  153,  and,  after  they 

*  See  page  53.  f  See  page  54. 


1 62  ANALYSIS  OF  IRON  AND  STEEL. 

are  all  lighted,  ten  minutes'  time  is  ample  to  burn  off  the  carbonaceous 
matter  in  the  boat  From  the  time  of  putting  in  the  boat,  fifty  minutes'  time 
is  ample  for  finishing  the  combustion,  including  the  displacement  of  the 
oxygen  by  air. 

The  time  required  when  using  a  porcelain  tube  is  somewhat  longer, 
owing  to  the  danger  incurred  of  cracking  the  tube  if  the  heat  is 
increased  or  diminished  too  rapidly.  A  platinum  tube  shorter  than 
the  one  here  figured  is  not  to  be  recommended,  as  it  cannot  contain 
enough  oxygen  to  burn  the  carbon  to  carbonic  acid,  and  a  consequent 
loss  is  often  unavoidable.  Duplicate  results  by  this  method  should 
rarely  vary  more  than  .005  of  a  per  cent,  carbon.  When  using  3 
grammes  of  the  sample,  the  percentage  of  carbon  is  obtained  by 
dividing  the  weight  of  carbonic  acid  by  n  and  multiplying  by  100. 

Instead  of  the  perforated  boat  and  holder  described  above,  the 
carbonaceous  residue  may  be  filtered  in  a  small  platinum  tube  fitting 
inside  the  combustion-tube.  It  is  made  as  represented  in  Fig.  76. 
The  small  perforated  disk  of  platinum  rests  on  a  seat  in  the 
tube  as  shown  in  the  sketch.  The  felt  on  the  disk  is  prepared 
in  the  same  way  as  directed  for  the  boat,  and,  after  drying  the 
carbonaceous  residue,  the  disk  is  moved  upward  in  the  filter- 
ing-tube, to  allow  the  gas  to  pass  through  the  filtering-tube 
during  the  combustion.  The  boat  has  several  advantages  over 
the  filtering-tube,  the  principal  one  being  that  the  boat  has  a 
much  larger  filtering-surface,  and,  besides,  there  is  no  danger 
of  the  felt  being  disturbed  during  the  filtering,  while  the  disk  in  the 
tube  may  be  loosened  in  its  seat  and  allow  some  of  the  carbonaceous 
matter  to  pass  around  it.  If  the  boats  when  not  in  use  are  kept 
carefully  covered,  the  same  felts  may  be  used  for  a  large  number  of 
filtrations ;  but  occasionally  they  become  clogged,  and  then  it  is  better 
to  renew  them. 

Instead  of  either  of  these  forms  of  filtering-apparatus,  a  simple 
glass  tube,  as  represented  in  Fig.  77,  may  be  used.  The  closely 
coiled  spiral  of  platinum  wire  fits  in  the  tube  as  shown  in  the  sketch. 
On  this  is  placed  a  rather  thick  layer  of  ignited  long-fibre  asbestos, 


DETERMINATION  OF   TOTAL    CARBON. 


i63 


and  ignited    asbestos   suspended   in   water   is  poured   over  it  to   make  a 
solid  felt.     The  tube  may  be  used  in  a  stand,  as  represented  in  Fig.  78, 

FIG.  77. 


FIG.  78. 


or  it  may  be  used  with  the  filter-pump  under  very  gentle  pressure. 
Filter  and  wash  the  carbonaceous  matter,  and  while  still  moist  transfer 
it  to  the  boat  (Fig.  79)  by  opening  out  the  sides  of  the  boat,  inverting 


FIG.  79. 


the  tube  over  it,  and  allowing  the  felt  and  spiral  to  slide  out  of  the 
tube.  Wipe  off  any  carbonaceous  matter  that  may  remain  on  the 
sides  of  the  tube,  or  that  may  have  adhered  to  the  spiral  in  removing 


164 


ANAL  YSIS   OF  IRON  AATD   STEEL. 


it,  with  little  wads  of  fibrous  asbestos  held  in  the  forceps  (Fig.  75). 
Place  these  wads  in  the  boat,  bend  the  sides  of  the  latter  into  their 
proper  shape,  dry  the  boat  and  contents  at  100°  C,  insert  the  boat 
in  the  porcelain  or  platinum  tube,  and  burn  off  the  carbonaceous 
matter  as  before  directed.  This  boat  is  made  by  cutting  a  piece  of 


FIG.  So. 


3.5 


platinum-foil    in  the  shape   shown   in   Fig.   80,   and    bending   it    up    over 
a  brass  former  into  the  shape  shown  in  Fig.  79. 

Instead  of  burning  the  carbonaceous  matter  in  a  current  of  oxygen, 
it  may  be  burned  by  sulphuric  and  chromic  acids  in  the  arrangement 
shown  in  Fig.  81.  P'  is  an  empty  U-tube,  O  is  a  tube  containing  silver 
sulphate  dissolved  in  strong  sulphuric  acid,  P  contains  anhydrous  cupric 
sulphate,  Q  granular  dried  calcium  chloride,  a  Liebig  bulb  and  drying- 
tube  R  constitute  the  absorption  apparatus,  S  is  the  safety-guard  tube,  and 
L,  L  constitute  the  arrangement  for  passing  air  through  the  apparatus. 
The  air  is  freed  from  carbonic  acid  in  passing  through  the  U-tube  M  filled 
with  lumps  of  fused  potassium  hydroxide.  Transfer  the  carbonaceous 
matter  and  asbestos  to  the  flask  A,  insert  the  stopper  carrying  the  bulb- 
tube  B,  close  the  stopcock  C,  and  connect  the  apparatus  as  shown  in  Fig. 
8 1,  including  the  weighed  absorption  apparatus.  See  that  the  joints  are 
all  tight,  and  then  pour  into  B  10  c.c.  of  a  saturated  solution  of  chromic 
acid,  admit  it  to  the  flask  A  by  opening  the  stopcock  C,  and  then  pour 
into  B  100  c.c.  strong  sulphuric  acid  with  a  little  chromic  acid  which  has 
been  heated  almost  to  boiling.  Let  this  run  into  A  slowly,  connect  the 


DETERMINATION  OF   TOTAL    CARBON. 


I65 


1 66  ANALYSIS    OF  IRON  AND   STEEL. 

air  apparatus  by  the  tube  N,  and  start  a  slow  current  of  air  through. 
Light  a  very  low  light  under  A,  and  increase  it  gradually  until  the  liquid 
is  heated  to  the  boiling-point.  Gradually  lower  the  light  while  the  cur- 
rent of  air  continues  to  pass,  and  when  about  I  litre  of  air  has  passed 
through  the  apparatus  after  the  light  is  extinguished,  detach  and  weigh 
the  absorption  apparatus,  with  the  precautions  mentioned  on  page  137. 
The  carbonaceous  residue  may  also  be  weighed  directly  instead  of 
being  burned  off.  In  this  method,  filter  on  a  Gooch  crucible  or  on 
counterpoised  filters,*  dry  at  IOO°  C,  and  weigh.  Burn  off  the  carbo- 
naceous matter  and  weigh  the  residue :  the  difference  between  the  two 
weights  is  carbonaceous  matter,  which  contains  about  70  per  cent,  of 
carbon  f  in  steel  or  iron  free  from  graphite.  Of  course  this  method  of 
direct  weighing  is  applicable  only  to  samples  when  all  the  carbon  is  in 
the  so-called  combined  condition. 

Modifications  by  Job  and  Davies.  \ 

The  following  are  the  principal  details  of  the  apparatus  (Fig.   82) : 
A'  combustion-furnace,  K,  nine  inches  in  length,  having  three  Bunsen 
burners  with  spreaders. 

A  Berlin  porcelain  combustion-tube,  G,  twenty  inches  in  length  and 
three-fourths  inch  inside  diameter,  containing  about  four  inches  in  length 
of  closely  rolled  copper  gauze,  I,  fitting  at  first  rather  loosely  in  the  tube, 
and  thoroughly  oxidized  prior  to  use, — exactly  as  in  the  old  method, — with 
pieces  of  clay  pipe  stem  between  the  cupric  oxide  and  the  end  of  the 
tube  to  prevent  the  former  from  being  forced  out  of  place  when  the  boat 
runs  up  against  it  in  the  determination.  A  piece  of  platinum-foil  as 
long  as  the  boat,  rolled  into  tubular  form,  fitting  closely  in  the  combustion- 
tube  and  pushed  into  place  next  to  the  cupric  oxide,  with  the  edges 
somewhat  bevelled  so  that  the  boat  when  quickly  pushed  in  with  the  wire 
will  run  up  smoothly  upon  the  foil.  This  contrivance  has  been  found  to 

*  See  page  29.  f  American  Chem.  Jour.,  iii.  245. 

J  Prepared  for  this  book  by  Messrs.  Robert  Job  and  Charles  T.  Davies  from  a  paper  read 
before  the  Philadelphia  Section  of  the  American  Chem.  Soc.,  September  13,  1900. 


DETERMINATION  OF   TOTAL    CARBON. 


1 67 


completely  prevent  cracking  of  the  por- 
celain tube,  even  when  a  cold  boat  is 
thrust  into  the  red-hot  tube. 

Asbestos  shields  at  H,  H,  through 
which  the  tube  passes,  prevent  possible 
heating  of  the  ends. 

A  six-inch  U-tube  containing  pieces  of 
thoroughly  dehydrated  cupric  sulphate 
about  one-eighth  inch  in  diameter  in  one 
arm,  F,  and  dehydrated  cuprous  chloride 
of  the  same  size  in  the  other,  E,  with  a 
small  piece  of  glass  wool  between  them 
and  also  upon  the  tops,  as  recommended 
by  Blair. 

A  small  bubble-tube,  D,  containing 
about  IO  c.c.  of  a  saturated  solution  of 
silver  sulphate  in  sulphuric  acid  of  1.40 
sp.  gr. 

A  four-inch  U-tube,  C,  containing 
thoroughly  dehydrated  granular  calcium 
chloride  in  particles  of  about  one-eighth 
inch  in  diameter,  free  from  powder. 

Potash  bulbs  B,  with  calcium  chloride 
tube  attached,  the  bulbs  being  about  one 
inch  in  diameter  and  one  and  a  quarter 
inches  high;  the  cluster  when  filled  ready 
for  use  containing  about  35  c.c.  of  potas- 
sium hydrate  (1.27  sp.  gr.),  and  weighing, 
including  the  calcium  chloride/about  80 
grammes;  the  calcium  chloride  tube  is 
about  two  and  a  quarter  inches  long  and 
one-half  inch  in  diameter. 

The  potash  bulbs  B'  are  exactly  the 
same  as  B,  but  the  calcium  chloride 


FIG.  82. 


1 68  ANALYSIS   OF  IRON  AND   STEEL. 

tube  remains  empty  and  serves  merely  to  prevent  any  possibility  of 
spattering  of  potassium  hydrate  solution  into  the  combustion-tube. 

The  three-way  cock  L  leads  to  the  oxygen  tank  N,  containing  oxygen 
free  from  hydrocarbons,  and  to  the  air-pressure  P,  the  latter  being 
produced  by  two  two-litre  bottles,  M  and  M',  and  the  pressure  regulated 
by  a  screw-clamp,  O. 

In  the  regular  determinations  3  grammes  of  steel  are  dissolved  in 
about  200  c.c.  of  double  chloride  of  copper  and  potassium  acidified  with 
hydrochloric  acid,  and  filtered  upon  a  platinum  boat,  washed  with  dilute 
hydrochloric  acid,  then  with  water,  and  dried  at  not  exceeding  no0  C. 
after  the  usual  manner. 

In  heating  the  furnace,  the  middle  burner  is  lighted  and  turned  up 
one-half  for  five  minutes,  then  full ;  at  the  same  time  the  two  other  burners 
are  turned  up  one-half,  and  after  five  minutes  given  the  full  flame.  The 
tube  will  be  red  hot  in  about  fifteen  minutes  from  the  start,  and  is  ready 
for  the  day's  determinations  without  further  attention. 

The  weighed  potash  bulbs  B  are  then  connected  in  place,  the  gum 
stopper  next  to  B'  removed,  and  the  boat  in  the  combustion-tube,  if 
present,  quickly  hooked  out  upon  a  porcelain  tile  with  a  copper  wire. 
The  oxygen  is  then  started  through  the  purifying  potash  bulbs  B'  at  the 
rate  of  about  four  bubbles  per  second,  the  dried  boat  for  the  determination 
removed  from  the  oven,  pushed  quickly  into  its  position,  and  the  gum 
stopper  inserted  promptly.  The  current  of  oxygen  is  then  let  pass  for 
seven  minutes  at  the  same  rate  of  speed,  though  only  about  three  minutes 
are  actually  required  ordinarily  for  the  combustion.  The  oxygen  is  then 
shut  off,  the  three-way  cock  turned,  and  the  air  passed  for  twelve  and  a 
half  minutes  at  the  rate  of  six  or  seven  bubbles  per  second,  or  as  fast 
as  the  bubbles  can  pass  and  remain  separate,  about  one  litre  of  air  being 
passed  in  this  time. 

The  entire  combustion  is  thus  finished  within  twenty  minutes,  when 
the  bulbs  are  removed  and  another  set,  previously  weighed,  are  connected 
and  the  second  combustion  proceeded  with. 

The  potash  bulbs  should  be  refilled  after  absorbing  about  2.5  grammes 
of  carbon  dioxide,  and  the  calcium  chloride  tube  at  the  same  time.  Care 


DETERMINATION  OF   TOTAL    CARBON.  169 

must  be  taken  to  have  the  calcium  chloride  thoroughly  dehydrated,  in 
small  eight-inch  granular  form,  without  powder,  and  shaken  down  as  com- 
pactly as  possible  by  tapping  lightly  with  the  finger  upon  the  tube  and 
filling  as  needed  until  full.  A  very  little  cotton  batting  is  placed  at  either 
end.  The  calcium  chloride  tube  C  immediately  preceding  the  weighed 
potassium  hydrate  bulbs  should  be  filled  in  the  same  manner,  and  should 
be  filled  with  freshly  dehydrated  calcium  chloride  after  about  fifty  deter- 
minations, or  when  the  calcium  chloride  in  the  end  nearest  the  silver 
sulphate  solution  becomes  slightly  moist. 

In  practice  the  greater  part  of  the  calcium  chloride  may  be  used  over 
and  over  again,  dehydrating  when  removed  by  heating  in  an  iron  or  porce- 
lain dish. 

The  copper  salts  in  the  U-tube  should  be  thoroughly  dehydrated  by 
heating  to  a  temperature  of  about  1 10°  C.  and  aspirating  slowly  with  air. 
This  can  be  accomplished  very  easily  by  placing  the  U-tube  flat  upon  the 
steam  table  and  attaching  slow  suction  for  about  one  hour.  This  should 
be  done  as  soon  as  the  cupric  sulphate  tends  to  become  blue  or  green  upon 
the  top  of  the  arm  F  of  the  U-tube.  When  ready  for  use  the  cupric 
sulphate  should  be  very  nearly  white  and  the  cuprous  chloride  a  dull  brown. 

It  is  very  advantageous  to  rechlorinate  the  solution  of  double  chloride 
of  copper  and  potassium  after  the  method  of  Dr.  Sargent,  as  detailed  in 
the  Journal  of  the  American  Chemical  Society,  vol.  xxii.  p.  210.  As  the 
solution,  however,  gradually  becomes  neutral,  we  find  it  desirable  to  make 
addition  of  hydrochloric  acid  after  rechlorinating  in  sufficient  amount  to 
restore  the  original  acidity  and  thus  prevent  the  separation  of  the  salts 
and  increase  rapidity  of  solution.  This  may  readily  be  done  by  titrating 
5  c.c.  of  the  rechlorinated  solution  with  standard  potassium  hydrate  solu- 
tion in  the  cold,  taking  as  the  end  reaction  the  point  at  which  the  ferric 
hydrate  formed  just  fails  to  go  into  solution  after  repeated  shaking. 
Titration  is  then  made  with  5  c.c.  of  a  solution  of  one  part  hydrochloric 
acid  to  thirteen  parts  water  (the  normal  acidity  of  the  double  chloride 
solution),  with  a  little  neutral  ferric  solution  as  indicator.  Comparison 
of  the  acidity  of  the  two  solutions  with  the  volume  of  the  solution  re- 
chlorinated  will  show  the  amount  of  hydrochloric  acid  needed. 


I/O  ANALYSIS   OF  IRON  AND   STEEL. 

As  to  the  accuracy  of  results,  we  have  checked  repeatedly  upon 
various  standard  steels  and  have  obtained  uniform  and  practically  identical 
results  with  those  obtained  by  the  regular  combustion  method  with 
platinum  tube. 

In  the  above  apparatus  a  number  of  details  have  been  taken  from  those 
presented  by  Dr.  G.  W.  Sargent,  Journal  of  the  American  Chemical  Society, 
vol.  xxii.  p.  277,  and  for  these  we  wish  to  make  hearty  acknowledgment. 

The  Repeated  Use  of  the  Double  Chloride  of  Copper  and  Potassium 
for  the  Solution  of  Steel  or  Iron  in  Estimating  Carbon.* 

In  the  Chemical  News,  vol.  Ixxix.  p.  169,  which  appeared  April  14  of  last 
year,  there  is  an  article  headed  "  The  Estimation  of  Carbon  in  Steel ;  Ap- 
paratus and  Materials,"  signed  J.  T.,  in  the  course  of  which  it  is  stated  that 
the  copper-ammonium  chloride  may  be  re-used  as  many  as  eight  times, 
provided  it  is  oxidized  by  drawing  air  through  it  after  each  solution,  and  pro- 
vided the  practice  of  allowing  the  sample  to  dissolve  overnight  is  adopted. 

Copper-potassium  chloride,  owing  to  its  freedom  from  organic  mat- 
ter, has  supplanted  the  ammonium  salt.  Most  chemists  use  the  former 
in  a  hydrochloric  acid  solution,  when,  by  the  aid  of  a  stirring  machine, 
the  drillings  are  dissolved  in  less  than  an  hour.  The  reaction  is 
expressed  in  the  following  equation : 

Fe  +  CuCl,  =  FeCl2  +  Cu  and  Cu  +CuCI,  =  Cu2Cl8. 

If  now  the  cuprous  chloride  be  oxidized  to  cupric,  there  is  no 
reason  why  the  double  chloride  solution  should  not  be  used  repeatedly 
until  the  accumulated  iron  salts  become  too  great.  As  stated  above, 
this  has  been  done,  but  the  time  consumed  in  oxidizing  by  a  current  of 
air  was  too  long  :  several  days  of  an  almost  continuous  current  of  air 
through  a  litre  of  the  acid  double  chloride  failed  to  completely  oxidize 
the  copper  salt.  The  source  of  my  air-current  was  a  filter-pump,  making 
the  waste  of  water  very  considerable.  Therefore,  I  decided  to  try  the 
effect  of  chlorinating  the  solution  direct. 

*  George  \V.  Sargent,  of  the  Carpenter  Steel  Company,  Reading,  Pennsylvania,  in  the  Journal 
of  the  American  Chemical  Society,  xxii.  210. 


DETERMINATION  OF   TOTAL    CARBON. 


The  result  has  been  most  agreeable.  At  the  present  time  we  have 
three  bottles  of  three  quarts'  capacity ;  in  one,  the  filtered  double  chloride 
ready  for  the  solution  of  the  drillings  is  kept ;  the  second  receives  the 
undiluted  filtrate  from  the  carbon ;  while  the  third,  filled  with  the  fil- 
trates, stands  in  the  corner  of  the  hood  with  a  current  of  chlorine  gas 
passing  through  it.  It  requires  just  a  day  to  chlorinate  three  quarts,  and 
that  is  about  the  amount  consumed  each  day.  When  chlorinated  the 
solution,  instead  of  being  of  a  dirty  brown,  has  almost  the  original  color 
of  copper-potassium  chloride.  After  standing  overnight  in  the  hood 
arid  being  filtered,  the  objectionable  odor  of  chlorine  is  gone  and  the 
solution  is  again  ready  for  use.  The  chlorinated  double  chloride  is  more 
energetic  in  its  solvent  action.  In  some  instances  the  solution  of  the 
drillings  has  been  accomplished  in  fifteen  minutes. 

As  many  as  eleven  solutions  have  been  made  with  one  quantity  'of 
the  double  chloride,  and  the  time  required  for  the  eleventh  solution  and 
filtration  was  very  little  longer  than  for  the  first. 

Combustion  in  the  Shinier  Crucible. 

In  this  apparatus  combustion  is  effected  in  a  special  water-jacketed 
platinum  crucible  (the  details  of  which  are  shown  in  Fig.  83)  closed  by  a 


FIG.  83. 


hollow  water-cooled  stopper  made  of  brass. 
An  ordinary  rubber  band  around  the  stop- 
per insures  a  tight  joint,  and  the  water 
passing  through  it  and  around  the  upper 
part  of  the  crucible  prevents  the  rubber 
from  softening  when  the  lower  half  of  the 
crucible  is  heated  to  a  high  temperature. 
For  combustion  of  carbon  from  steel  or 
pig-iron  air  alone  is  used.  Other  novel 
parts  of  the  apparatus  are  a  small  brass 
tube  for  cupric  oxide ;  a  glass  tube  filled 
with  glass  beads,  wet  with  water,  for  retain- 
ing hydrochloric  acid  and  chlorine ;  and  a  special  funnel  for  rapid  filtration 
and  transference  of  the  carbon. 


1/2  ANALYSIS  OF  IRON  AND  STEEL. 

Beginning  at  the  left,  Fig.  84,  the  train  of  apparatus,  conveniently  dis- 
posed on  a  heavy  asbestos  board  shelf,  is  as  follows : 

For  air-pressure,  a  large  aspirator  bottle,  A,  filled  with  distilled  water,  and 
connected  with  a  lower  bottle,  B,  by  means  of  a  tube  reaching  to  the  bot- 
tom of  the  latter.  C,  potassium  hydroxide  bulbs.  D,  a  small  guard  bottle. 
The  crucible,  E,  connected  with  a  water  supply,  K,  and  waste,  L.  The 
crucible  is  supported  by  passing  it  about  half-way  through  a  heavy  piece  of 
asbestos  board.  Under  the  crucible  an  adjustable  Bunsen  burner  or  an 

FIG.  84. 


upright  blast-lamp.  A  brass  tube,  F,  containing  rather  fine  cupric  oxide, 
but  free  from  powder,  in  its  central  portion,  is  heated  to  a  red  heat  by  a 
special  burner,  for  about  two  inches.  This  tube  is  twelve  inches  long  and 
is  T73-  inch  in  external  diameter.  Attachments  are  made  by  passing  the 
rubber  tubing  over  the  ends  of  the  tube  which  is  supported  in  a  rectan- 
gular opening  in  the  shelf.  The  ends  of  the  tube  are  cooled  by  a  long 
piece  of  heavy  blotting-paper  fastened  around  each  end  and  dipping  into 
the  water  contained  in  tin  boxes  attached  to  the  shelf.  The  glass-bead 
tube,  G,  internally  wet  with  distilled  water  and  externally  cooled  by  wet 
filter-paper,  for  retaining  hydrochloric  acid  and  chlorine.  A  large  calcium 
chloride  tube,  H.  Potassium  hydroxide  bulbs  and  drying  tube,  I.  A 
guard-tube  of  calcium  chloride,  J. 

The  carbon  is  filtered  on  a  filter-tube  ^  inch  in  internal  diameter.     A 
small  glass  rod,  flattened  out  at  the  end,  passes  through  the  stem  of  the 


DETERMINATION  OF  TOTAL  CARBON.  1/3 

funnel  and  projects  several  inches  beyond.  A  mass  of  glass  wool  J^  inch 
deep  is  packed  into  the  bottom  of  the  tube,  and  on  this  is  deposited,  under 
suction,  the  filter,  about  l/&  inch  deep,  of  finely  divided  ignited  asbestos. 
After  filtration  and  washing  the  contents  of  the  tube  are  pushed  up  by 
means  of  the  projecting  glass  rod  until  the  filter  projects.  The  filter  can 
now  be  easily  picked  off  the  glass  wool  base  by  use  of  a  curved  forceps. 
The  carbon  may  be  quickly  and  conveniently  dried  by  placing  the  filter 
upon  a  previously  warmed  and  labelled  scorifier. 

In  direct  combustions  of  difficultly  soluble  alloys  mix  0.2  gramme  of 
the  finely  pulverized  sample  with  2.5  grammes  of  pulverized  lead  chromate, 
place  the  mixture  in  a  porcelain  crucible,  cover  with  0.5  gramme  of  the 
chromate,  and  heat  for  an  hour  in  a  current  of  oxygen. 

2.    Solution  of  the  Iron  in  Cupric  Sulphate,  Filtration,  and  Combustion 
of  the  Residue  in  a  Boat  in  a  Current  of  Oxygen. 

To  3  grammes  of  steel  in  a  400  c.c.  beaker  add  150  c.c.  of  solution 
of  cupric  sulphate,  made  by  dissolving  200  grammes  of  the  copper 
salt  in  water,  adding  a  dilute  solution  of  caustic  soda  until  a  slight 
permanent  precipitate  appears,  allowing  it  to  settle,  filtering  through 
asbestos,  and  diluting  to  I  litre.  For  pig-iron,  spiegel,  and  ferro- 
manganese,  use  I  gramme,  and  50  c.c.  of  cupric  sulphate  solution. 
Heat  the  solution  gently,  and  stir  well  until  decomposition  is  com- 
plete. Filter  in  a  glass  filtering-tube  on  asbestos,  as  described  on 
page  162.  Wash  well  with  water,  transfer  to  a  boat,  as  directed 
on  page  163,  dry,  and  burn  in  a  porcelain  tube,  as  directed  on 
page  154.  The  results  are  apt  to  be  a  little  low,  owing  to  the 
difficulty  of  thoroughly  oxidizing  the  mass  of  copper  mixed  with  the 
carbonaceous  matter. 

Instead  of  filtering  off  the  mass  of  copper,  carbonaceous  matter, 
etc.,  decant  the  clear  supernatant  fluid  through  the  filtering-tube,  wash 
several  times  by  decantation,  and  then  dissolve  the  copper  in  potassium- 
cupric  chloride,  cupric  chloride,  or  ferric  chloride.  Filter,  wash  the 
residue  with  a  little  dilute  hydrochloric  acid,  and  then  with  cold 
water,  transfer  to  a  boat,  and  burn  as  directed  on  page  154  et  seq. 


174-  ANALYSIS  OF  IRON  AND  STEEL. 

3.    Solution    of  the    Iron    in    Cupric   Sulphate,    and   Oxidation   of  the 
Residue,  by  Chromic  and  Sulphuric  Acids. 

Treat  the  sample  with  solution  of  cupric  sulphate,  as  in  the 
method  just  described.  Allow  the  precipitated  copper  and  carbo- 
naceous matter  to  settle,  pour  off  the  clear  supernatant  liquid,  and 
transfer  the  residue  to  the  flask  A  (Fig-.  81,  page  165)  by  means  of 
a  platinum  spatula  and  a  fine  jet  of  water.  The  water  used  should 
not  exceed  20  or  25  c.c.*  The  apparatus  is  that  sketched  in  Fig.  81, 
the  only  difference  being  that  the  tube  O  contains  merely  a  little  strong 
sulphuric  acid.  Effect  the  combustion  exactly  as  described  on  page  164. 

DETERMINATION   OF  GRAPHITIC  CARBON. 

Karsten  gave  the  first  information  in  regard  to  the  existence  of  graphite 
in  pig-iron,  and  he  suggested  dissolving  the  sample  in  nitric  acid  with  the 
addition  of  a  few  drops  of  hydrochloric  acid,  in  hydrochloric  acid  alone, 
or  in  dilute  sulphuric  acid,  boiling  the  residue  with  caustic  potash,  filtering, 
washing  again  with  hydrochloric  acid  and  finally  with  water,  and  weighing 
the  residue  as  graphite.  A  very  interesting  comparison  of  the  results 
obtained  by  the  use  of  different  solvents  is  given  by  Drown.*  The  usual 
method  is  as  follows.  Treat  I  gramme  of  pig-iron  or  10  grammes  of  steel 
with  an  excess  of  hydrochloric  acid  (i.i  sp.  gr.).  When  all  the  iron  is  dis- 
solved, boil  for  a  few  minutes,  allow  the  graphite  to  settle,  and  decant  the 
supernatant  fluid  on  an  asbestos  filter,  using  either  the  perforated  boat,  Fig.  73, 
or  the  filtering-tube,  Figs.  77  and  78.  Wash  several  times  with  hot  water  by 
decantation,  then  pour  on  the  residue  in  the  beaker  30  c.c.  of  a  solution 
of  caustic  potash  (sp.  gr.  i.i),  and,  when  the  effervescence  ceases,  heat 
the  solution  to  boiling.  Filter  on  the  same  filter,  transfer  the  graphite 
etc.,  to  the  filter,  .wash  with  hot  water  again,  and  finally  with  alcohol 
and  ether.  Burn  the  graphite  by  one  of  the  methods  given  under 
"  Determination  of  Total  Carbon,"  and  from  the  weight  of  carbonic 
acid  obtained  calculate  the  percentage  of  carbon  existing  as  graphite. 

*  Trans.  Inst.  Min.  Engineers,  iii.  42. 


DETERMINATION  OF  COMBINED  CARBON.  1/5 

It  frequently  happens,  when  the  sample  is  a  high  steel,  that  the  residue 
which  remains  after  treating  it  as  above  is  black,  and  contains  carbon, 
but  it  is  not  crystalline  in  appearance,  and  bears  no  resemblance  to 
graphite.  The  same  steel  will  dissolve  completely  in  nitric  acid,  and 
when  filtered  will  not  leave  a  trace  of  carbon  on  the  felt.  Steels  con- 
taining graphite  give  appreciably  less  carbon  when  dissolved  in  nitric 
acid  than  when  dissolved  in  hydrochloric  acid.  The  method  giving 
probably  the  most  accurate  and  certainly  the  most  uniform  results  is  as 
follows.  Dissolve  the  weighed  sample  in  nitric  acid  (sp.  gr.  1.2),  using  15 
c.c.  of  acid  to  each  gramme  taken  for  analysis.  Filter  on  the  perforated 
boat  or  on  an  ignited  asbestos  filter,  in  a  glass  tube,  transfer  the  residue 
to  the  filter,  and  wash  thoroughly  with  hot  water.  Treat  the  residue  on 
the  filter  with  hot  caustic  potash  solution,  1. 1  sp.  gr.  (as  the  silicon  is  all 
oxidized  to  silica  there  will  be  no  effervescence),  wash  thoroughly  with  hot 
water,  then  with  a  little  dilute  hydrochloric  acid,  and  finally  with  hot  water. 
Burn  the  carbon  by  one  of  the  methods  previously  mentioned  and  calculate 
the  carbonic  acid  obtained  to  carbon,  and  call  the  result  graphite* 

DETERMINATION    OF    COMBINED    CARBON. 

Indirect  Method. 

Having  determined  the  total  carbon  and  the  graphite,  by  subtracting 
the  latter  from  the  former  we  obtain  the  amount  of  carbon  existing  in  the 
combined  condition. 

Direct  Method. 

This  method  was  first  introduced  by  Eggertzf  in  1862.  It  is  based 
on  the  fact  that  when  steel  containing  carbon  is  dissolved  in  nitric  acid 
(1.2  sp.  gr.),  the  carbon,  which  sometimes  at  first  separates  out  in  flocks 
of  a  brownish  color,  is  eventually  dissolved,  giving  to  the  solution  a  depth 

*  Shimer  (Jour.  Amer.  Chem.  Soc.,  xvii.  873)  has  shown  that  titanium  carbide  is  insolu- 
ble in  dilute  hydrochloric  acid  and  that  the  nitric  acid  method  is  the  only  accurate  one  for  the 
determination  of  graphite. 

f  Jern-Kontorets  Annaler,  1862,  p.  54;  1874,  p.  176;  1881,  p.  301  ;  Chem.  News,  vii.  254; 
xliv.  173. 


1/6  ANAL  YSIS  OF  IRON  AND  STEEL. 

of  color  directly  proportionate  to  the  amount  of  combined  carbon  in  the 
steel.  To  use  this  in  practice  it  is  only  necessary  to  determine  accurately 
the  amount  of  combined  carbon  contained  in  a  steel,  by  a  combustion 
method,  and  to  compare  the  depth  of  color  in  a  solution  of  this  standard 
with  that  of  any  unknown  steel,  in  order  to  ascertain  the  amount  of 
carbon  in  the  latter.  There  is,  however,  a  limitation  to  the  application  of 
this  method.  Reference  was  made  on  page  132  to  the  fact  that  combined 
carbon  is  now  believed  to  exist  in  two  conditions  in  steel,  or  rather  that 
under  certain  circumstances  a  portion  of  the  combined  carbon  changes  its 
condition,  and,  from  a  chemical  point  of  view,  while  it  is  still  combined 
caibon,  in  that  it  is  soluble  in  nitric  acid,  it  fails  to  impart  so  dark  a  color 
to  its  nitric  acid  solution  as  it  did  in  its  original  state.  The  circumstances 
under  which  a  change  of  this  kind  occurs  are  quite  well  known,  and  are 
merely  those  occasioned  by  the  mechanical  treatment  to  which  steel  is 
submitted,  such  as  hammering,  rolling,  hardening,  tempering,  etc.*  It 
may  be  stated,  then,  as  a  general  proposition,  that  the  standard  steel  for 
the  color-test  should  be  of  the  same  kind  and  in  the  same  pJiysical  condition 
as  the  samples  to  be  tested. 

To  obtain  the  best  results  samples  should  be  taken  from  the  original 
ingots  which  have  not  been  reheated,  rolled,  or  hammered  ;  Bessemer 
steel  should  be  compared  with  Bessemer,  crucible  with  crucible,  open 
hearth  with  open  hearth ;  the  standard  should  contain  approximately  the 
same  amount  of  carbon  as  the  samples  to  be  tested,  and  should  have  as 
nearly  as  possible  the  same  chemical  composition.  The  only  elements 
that  seem  to  have  any  decided  effect  on  the  color  of  the  nitric  acid 
solution  are  copper,  cobalt,  and  chromium. 

Weigh  out  carefully  .2  gramme  of  each  sample,  including  the 
standard,  into  test-tubes  6  inches  (150  mm.)  long  and  ^  inch  (16  mm.) 
in  diameter.  The  test-tubes  should  be  perfectly  clean  and  dry,  and  each 
one  marked  with  the  number  of  the  sample  on  a  small  gummed  label 
near  the  top.  A  little  wooden  rack  (Fig.  85)  is  convenient  for  holding 

*  Two  very  interesting  papers  on  this  subject  will  be  found  in  the  Chem.  News,  J.  S.  Parker^ 
"On  the  Varying  Condition  of  Carbon  in  Steel,"  xlii.  88;  T.  W.  Hogg,  "  On  the  Condition  of 
Carbon  in  Steel,"  xlii.  130. 


DETERMINATION  OF  COMBINED  CARBON. 


177 


FIG.  85. 


the  test-tubes  in  the  weighing-room,  and  to  avoid  all  chance  of  error 
the  tube  is  not  placed  in  the  rack  until  the  sample  has  been  weighed 
and  is  ready  to  be  transferred.  A  little  platinum  or  aluminum  dish 
about  I T/2,  inches  (40  mm.)  in  diameter,  with  a  spout,  and  furnished  with 

a  counterpoise  (Fig.  44,  page  36), 
is  very  convenient  for  holding  the 
drillings,  which  are  brushed  from 
it  into  the  test-tube  with  a  cafnel's- 
hair  brush.  A  very  excellent  form 
of  water-bath  is  shown  in  Fig.  86. 
It  may  be  provided  with  a  con- 
stant level  arrangement,  consisting 

of  a  tubulated  bottle,  the  height  of  the  end  b  of  the  vertical  tube  a 
fixing  the  level  of  the  water  in  the  bath.  A  is  the  bath  and  B  the  rack. 


FIG.  86. 


The  top  of  the  rack  is  of  sheet-copper,  perforated  to  receive  the  test- 
tubes,  the  bottoms  of  which  rest  on  the  coarse  copper  gauze,  which  is 
joined  to  the  top  by  the  uprights  C.  The  top  of  the  rack  rests  on  a 
flange  around  the  top  of  the  bath. 

Place  the  test-tubes  in  the    rack  B,  and    stand  the    rack  in  the  bath 


ANAL  YSIS  OF  IRON  AND  STEEL. 


FIG.  87. 


which  contains  cold  water.  Drop  into  each  test-tube,  from  a  pipette,  the 
proper  amount  of  nitric  acid  (sp.  gr.  1.2).  For  steels  containing  less  than 
.3  per  cent,  carbon  use  3  c.c.  nitric  acid;  from  .3  to  .5  per  cent,  carbon, 
4  c.c. ;  from  .5  to  .8  per  cent.,  5  c.c.;  from  .8  to  I  per  cent.,  6  c.c.;  and 
over  I  per  cent.,  7  c.c.  An  insufficient  amount  of  acid  gives  the  solution 
a  slightly  darker  tint  than  it  should  properly  have. 

The  apparatus  shown  in  Fig.  87*  is  useful  for  the  rapid  addition  of 
measured  quantities  of  nitric  acid  to  the  samples. 

It  consists  of  a  glass  reservoir  holding  750  c.c.,  communicating  below 
with  four  burettes  graduated  to  deliver  various  quan- 
tities of  acid  up  to  10  c.c.  Each  burette  is  furnished 
with  a  loose-fitting  glass  cap.  The  burettes  are  fitted 
with  three-way  glass  stopcocks,  so  that  a  quarter  of 
a  revolution  connects  them  with  the  reservoir,  and 
when  the  proper  amount  of  acid  has  run  in,  the  stop- 
cock is  turned  another  quarter,  which  shuts  off  the 
reservoir  and  completely  empties  the  burette,  thus  de- 
livering the  exact  amount  of  acid  measured  into  the 
test-tube  containing  the  weighed  sample  of  steel  in 
which  carbon  is  to  be  determined. 

As  shown  in  the  cut,  each  test-tube  stands  in  a 
bottle  of  cold  water  to  prevent  too  violent  action  of  the 
acid  during  solution.  The  whole  apparatus  is  mounted 
on  a  rotary  stand,  and,  as  used  at  the  laboratory  of  the 
Bethlehem  Iron  Company,  is  contained  in  a  small  hood 
near  the  drill  and  balance  described  on  page  16,  so 
that  the  operator,  seated  on  a  revolving  stool,  can  add  acid  to  one  sam- 
ple of  steel  while  the  drillings  of  the  next  sample  are  falling  into  the 
balance-pan. 

The  apparatus,  as  here  shown,  is  a  modification  by  Mr.  Albert  L. 
Colby,  of  the  Bethlehem  Iron  Company,  of  an  apparatus  first  designed 
by  Mr.  E.  A.  Uehling  in  1884. 


Communicated  to  the  author. 


DETERMINATION  OF  COMBINED  CARBON.  1/9 

The  nitric  acid  is  made  by  adding  its  own  volume  of  water  to  acid 
of  the  usual  strength  (1.4  sp.  gr,).  It  should  be  absolutely  free  from 
chlorine  or  hydrochloric  acid,  as,  according  to  Eggertz,  .0001  gramme 
chlorine  in  a  nitric  acid  solution  of  .1  gramme  iron  in  2.5  c.c.  nitric  acid 
gives  a  decidedly  yellow  color.  The  nitric  acid  should  be  added  slowly, 
to  prevent  violent  action,  and  the  drillings  should  not  be  too  fine,  for 
the  same  reason.  Place  in  the  top  of  each  test-tube  a  small  glass  bulb  * 
or  a  very  small  funnel,  heat  the  water  in  the  bath  to  boiling,  and  boil 
until  all  the  carbonaceous  matter  is  dissolved,  shaking  the  tubes  from 
time  to  time  to  prevent  the  formation  of  a  film  of  oxide.  The  time 
required  for  solution  is  for  low  steels  about  twenty  minutes  and  for  high 
steels  (over  I  per  cent,  carbon)  forty-five  minutes.  After  entire  solution 
of  the  carbonaceous  matter,  prolonged  heating  tends  to  make  the  color 
lighter;  therefore,  as  soon  as  the  absence  of  small  bubbles  and  the  dis- 
appearance of  any  brownish  flocculent  matter  show  complete  solution, 
remove  the  rack  from  the  bath  and  stand  it  in  a  dish  of  cold  water. 
The  dish  should  be  about  the  same  size  as  the  bath,  so  that  the  top 
will  be  covered  by  the  top  of  the  rack,  thus  excluding  the  light  from 
the  solutions,  in  which  case  the  color  will  not  fade  for  a  long  time. 
Under  all  circumstances  the  solutions  should  be  kept  out  of  the  light, 
and  especially  out  of  direct  sunlight,  as  much  as  possible.  If  there 
should  be  necessarily,  in  the  steels  operated  on  at  one  time,  a  wide 
range  in  carbon,  the  test-tubes  should  be  removed  from  the  bath  as  fast 
as  their  respective  contents  are  dissolved  and  placed  in  cold  water  in  a 
dark  place.  The  appearance  of  the  drillings  will  often  give  an  idea  of 
the  approximate  carbon  contents  of  a  sample,  but  when  there  is  no  clue 
whatever,  it  is  best  to  begin  by  adding  3  c.c.  nitric  acid  to  the  weighed 
portion  in  the  test-tube,  and  increase  the  amount  i  c.c.  at  a  time  as  the 
depth  of  color  of  the  solution  or  the  amount  of  flocculent  carbonaceous 
matter  indicates  a  higher  carbon  percentage.  To  compare  the  colors  of 


*  These  bulbs  are  easily  made  by  sealing  one  end  of  a  glass  tube  in  the  blow- pipe  flame,  heating 
it,  blowing  a  bulb  of  the  proper  size,  allowing  it  to  cool,  heating  it  above  the  neck,  and  drawing  it 
out  as  shown  in  Fig.  85. 


180  ANALYSIS  OF  IRON  AND  STEEL. 

the  solutions,  pour  the  standard  into  one  of  the  carbon  tubes  (Fig.  88), 
wash  out  the  test-tube  with  a  little  cold  water,  add  it  to  the  solution 
in  the  carbon  tube,  and  dilute  to  a  convenient  amount. 

This  dilution  should  be  sufficient  to  make  the  volume  of  the  FIG.  88. 
diluted  standard  at  least  twice  as  great  as  the  volume  of  acid 
originally  used  to  dissolve  the  sample,  as  this  amount  of  water 
is  necessary  to  destroy  the  color  due  to  the  ferric  nitrate.  It 
should  not,  however,  greatly  exceed  this  amount,  and  should  be 
some  convenient  multiple  of  the  carbon  contents  of  the  standard 
in  tenths  of  a  per  cent.  Thus,  if  a  standard  contains  .45  per 
cent,  carbon,  dilute  the  solution  in  the  carbon  tube  to  9  c.c ,  then 
each  c.c.  will  equal  .05  per  cent.  The  carbon  tubes  should  be 
y2  inch  (12  mm.)  in  diameter,  holding  at  least  30  c.c.,  and  grad- 
uated to  yV  c.c.  The  tubes  should  have  exactly  the  same  diam- 
eter, and  the  glass  should  be  perfectly  colorless  and  have  walls 
of  the  same  thickness.  They  should,  of  course,  be  most 
accurately  graduated. 

Mr.  E.  F.  Wood,*  of  the  Homestead  Works,  leaves  the  lower 
ends  of  the  tubes  free  from  graduations  to  give  a  clear  space  for 
comparing  the  colors.  He  considers  this  especially  necessary  in 
low  steels,  for  which  he  uses  I  gramme  of  the  sample,  dissolves 
in  25  c.c.  of  nitric  acid,  boils  for  from  five  to  seven  minutes  in  a 
glycerine  bath  at  140°  C,  and  compares  in  tubes  ^  inch  (18  mm.) 
in  diameter. 

The  standard  having  been  prepared,  pour  the  solution  of  the  sample 
to  be  tested  into  another  carbon  tube,  rinse  the  test-tube  into  it  with  a 
little  cold  water,  and  compare  the  colors.  If  the  solution  of  the  sample 
is  darker  than  that  of  the  standard,  add  water  little  by  little,  shaking  the 
tube  well  to  mix  the  solution  until  the  shades  are  exactly  the  same. 
Allow  a  minute  or  two  for  the  solution  to  run  down  the  walls  of  the 
tube,  and  read  the  volume.  If  the  standard  was  diluted  as  above,  then, 
of  course,  each  c.c.  will  equal  .05  per  cent,  carbon,  and  if  the  volume  of 

*  Communicated  to  the  author. 


DETERMINATION  OF  COMBINED  CARBON. 


181 


FIG.  89. 


the  sample  is  10.5  c.c.  it  will  contain  .525  per  cent,  carbon.  If  the  solu- 
tion of  the  sample  when  first  transferred  to  the  tube  should  be  lighter 
in  color  than  the  standard,  a  lower  standard  must  be  used,  or  this  one 
may  be  diluted  to,  say,  13.5  c.c.,  in  which  case  the  number  of  c.c. 
divided  by  3  will  give  the  percentage  of  carbon  in  tenths.  The  color 

may  be  compared  by  holding  the  two 
tubes  in  front  of  a  piece  of  white  paper 
held  towards  the  light,  but  a  camera 
made  of  light  wood  and  blackened 
inside  is  most  convenient,  and  at  night  is 
quite  invaluable.  It  is  shown  in  Fig.  89, 
and  consists  of  a  box  3^  inches  (90 
mm.)  high  inside,  \y2  inches  (38  mm.) 
wide  at  one  end,  and  5  inches  (127  mm.) 
at  the  other.  It  is  24  inches  (610 
mm.)  long,  and  is  supported  on  a  rod, 
which  can  be  raised  and  lowered  to  suit 
the  convenience  of  the  observer.  The 
small  end  is  closed  by  a  piece  of  ground 

glass,  which  slides  in  through  a  slot  on  top  I  inch  (25  mm.)  from  the 
end.  Immediately  beyond  this  is  another  slot  to  receive  a  thin  piece  of 
faintly  blue  glass,  which  is  inserted  when  the  tests  are  made  at  night, 
using  an  oil-lamp  placed  on  a  stand  just  beyond  the  camera.  In  fact, 
in  many  steel-works,  to  avoid  the  differences  between  the  colors  as  seen 
by  daylight  and  lamplight,  all  comparisons  are  made  in  a  dark  room, 
using  a  box  or  camera  and  an  oil-lamp.  Two  holes  in  the  top  of  the 
camera  just  inside  the  ground-glass  screen  receive  the  carbon  tubes,  the 
ends  of  which  rest  on  a  piece  of  black  cloth  on  the  bottom  of  the 
camera  inside.  Another  piece  of  black  cloth  fastened  across  the  top  of 
the  camera,  covering  the  top  of  the  ground-glass  slide,  and  having  holes 
just  large  enough  to  admit  the  tubes,  excludes  all  light  except  that  at 
the  back  of  the  tubes.  A  north  light  is  much  the  best  for  comparing 
the  colors,  and,  as  to  most  observers  the  left-hand  tube  appears  a  little 
the  darker,  the  color  will  be  exactly  matched  when,  the  tubes  being 


1 82  ANALYSIS  OF  IRON  AND  STEEL. 

reversed,  the  left-hand  tube  still  appears  a  little  the  darker  of  the 
two. 

Instead  of  diluting  the  solutions  to  agree  with  a  standard,  as  above 
described,  some  chemists  use  a  rack  of  permanent  standards,  as  suggested 
by  Britton.*  The  principal  difficulty  heretofore  attending  the  use  of  per- 
manent standards  has  been  the  impossibility  of  preventing  their  fading; 
but,  according  to  Eggertz,f  this  is  now  entirely  overcome  by  the  method 
of  preparing  them  suggested  by  Prof.  F.  L.  Ekman.  The  details  are  as 
follows.  Dissolve  3  grammes  of  neutral  ferric  chloride  in  100  c.c.  water 
containing  1.5  c.c.  hydrochloric  acid;  dissolve  2.1  grammes  cupric  chloride 
in  100  cc.  water  containing  .5  c.c.  hydrochloric  acid,  dissolve  2.1  grammes 
cobaltic  chloride  in  100  c  c.  water  containing  5  c.c.  hydrochloric  acid, 
using  the  neutral  salts  in  all  cases.  These  solutions  will  contain  about 
.01  gramme  of  the  metal  to  the  c.c.,  and  by  adding  to  8  c.c.  of  the  iron 
solution  6  c.c.  of  the  cobalt  solution,  3  c.c.  of  the  copper  solution,  and 
5  c.c.  water  containing  .5  per  cent,  hydrochloric  acid,  a  liquid  is  obtained 
which  has  a  color  approximating  that  obtained  by  dissolving  .2  gramme 
of  steel,  containing  I  per  cent,  of  carbon,  in  nitric  acid,  and  diluting  to 
10  c.c.,  or  .1  per  cent,  carbon  to  the  c.c.  Prepare  a  number  of  test-tubes 
of  the  size  described  on  page  176,  but  in  this  case  it  is  essential  that 
they  should  be  of  exactly  the  same  diameter,  and  that  the  glass  should 
be  as  nearly  colorless  as  possible.  By  successive  dilutions  with  water 
containing  .5  per  cent,  hydrochloric  acid,  of  the  normal  solution  prepared 
as  above,  make  solutions  of  about  the  proper  strength  for  the  series 
required. 

The  variations  should  be  about  .02  per  cent,  between  the  different 
tubes  of  the  series,  corresponding  to,  say,  the  even  hundredths.  There 
should  be  about  10  c.c.  of  solution  in  each  tube,  and  then  the  color 
of  each  should  be  compared  with  a  standard  steel,  diluted  to  the  exact 
strength  required  in  the  permanent  standard.  For  example,  if  the  standard 
steel  contains  .4  per  cent,  carbon,  and  you  wish  to  get  the  exact  color 
for  the  .32  per  cent,  carbon  tube  in  the  permanent  series,  dissolve  .2 

*  Chem.  News,  xxii.  101.  f  Ibid.,  xliv.  173. 


DETERMINATION  OF  COMBINED  CARBON.  183 

gramme  of  the  standard  exactly  as  directed  on  page  178,  pour  the 
solution  into  a  carbon  tube,  and  dilute  it  in  accordance  with  the  formula, 
carbon  required  :  carbon  of  standard  ::  IO  c.c.  :  fhe  number  of  c.c.  re- 
quired, or,  in  this  case,  32  :  40  : :  10  c.c.  :  12.5  c.c.  Therefore  dilute 
the  solution  in  the  carbon  tube  to  12.5  c.c.,  pour  10  c.c.  into  a  test-tube 
exactly  like  those  used  for  the  permanent  standards,  and  compare  it  with 
the  .32  per  cent,  carbon  tube.  If  the  color  of  the  permanent  solution 
is  not  exactly  the  same,  correct  it  by  adding  portions  of  the  solutions 
of  the  iron,  cobalt,  or  copper  salts,  or  water  containing  .5  per  cent, 
hydrochloric  acid.  The  iron  salt  or  hydrochloric  acid  ^.lone  gives  a 
yellowish,  the  cobalt  salt  a  brownish,  and  the  copper  salt  a  greenish, 
tone  to  the  solution.  The  standards  may  now  be  arranged  in  a  rack, 
as  shown  in  Fig.  90.  The  colors  of  the  permanent  standards  once 

FIG.  90. 


fixed,  the  samples  to  be  analyzed  are  treated  exactly  as  described  on 
page  178,  the  test-tubes  used  being  precisely  like  those  containing  the 
permanent  standards,  and  each  one  carefully  graduated  to  contain  10  c.c. 
When  the  samples  (.2  gramme  each)  are  dissolved  and  cooled,  dilute 
each  solution  in  turn  with  cold  water  to  10  c.c.,  mix  thoroughly,  and 
compare  it  with  the  standards  in  the  rack,  •  by  which  means  the  carbon 
may  be  estimated  to  the  nearest  hundredth  of  a  per  cent. 

In  testing  white  cast  iron,  use  only  .05  gramme,  dissolve  in  7  c.c. 
nitric  acid,  dilute  the  standard  to  some  convenient  amount  approxi- 
mating 20  c  c.,  and  compare  as  quickly  as  possible  to  avoid  the  precipi- 
tation of  carbonaceous  matter,  which  is  apt  to  occur  under  these 
circumstances.  The  graphite  in  ordinary  gray  pig-iron,  and  sometimes 
even  in  steels,  renders  filtration  necessary.  In  this  case  add  to  the 
cold  acid  solution  one-half  of  its  volume  of  water,  filter  through  a 
small,  dry,  ashless  filter  into  the  carbon  tube,  wash  with  as  little 
water  as  possible,  and  compare  as  usual. 


1 84  ANAL  YSIS  OF  IRON  AND  STEEL. 

DETERMINATION    OF   TITANIUM. 

By  Precipitation. 

Only  traces  or  very  minute  amounts  of  titanium  are  found  in  steel,  but 
notable  quantities  exist  in  some  kinds  of  pig-iron.  As  pointed  out  by 
Riley,*  when  pig-iron  containing  titanium  is  dissolved  in  hydrochloric 
acid  a  portion  of  the  titanium  goes  into  solution,  while  the  remainder 
is  found  with  the  insoluble  matter.  The  insoluble  portion,  as  noticed 
on  page  85  et  seq.,  contains  phosphoric  acid.  It  is  a  curious  fact  that 
as  titanic  acid  interferes  with  the  determination  of  phosphoric  acid  by 
its  tendency  to  form  upon  evaporation  to  dryness  an  insoluble  phos- 
pho-titanate,  so  phosphoric  acid  interferes  with  the  determination  of 
titanic  acid  by  partially  preventing  the  precipitation  of  titanic  acid 
from  its  boiling  sulphuric  acid  solution.  The  best  method,  therefore, 
for  the  determination  of  titanium  is  to  proceed  exactly  as  for  the  de- 
termination of  phosphorus  when  titanium  is  present,  as  directed  on 
page  85  et  seq.,  until  the  residue  from  the  aqueous  solution  of  the 
sodium  carbonate  fusion  is  obtained.  Dry  this  residue,  transfer  it  to  a 
large  platinum  crucible,  preferably  the  one  in  which  the  sodium  carbonate 
fusion  was  made,  burn  the  filter,  add  its  ash  to  the  residue,  and  fuse  the 
whole  with  fifteen  or  twenty  times  its  weight  of  potassium  bisulphate. 
In  fusing  with  potassium  bisulphate  it  is  necessary  to  begin  with  a  very 
low  heat,  and  to  raise  the  temperature  very  slowly  and  carefully  to  a 
low  red  heat,  as  the  mixture  has  a  strong  tendency  to  boil  over  the  top 
of  the  crucible  whenever  the  temperature  is  increased  too  rapidly. 
When  the  lid  of  the  crucible  is  raised,  fumes  of  sulphuric  anhydride 
should  come  off,  and  the  fusion  should  be  kept  at  this  point  for  several 
hours,  or  until  it  is  quite  clear  and  the  whole  of  the  ferric  oxide  has 
been  dissolved.  Allow  the  fused  mass  to  cool,  add  to  it  from  10  c.c.  to 
20  c.c.  of  strong  sulphuric  acid,  and  heat  until  it  is  perfectly  liquid.  When 
cold  it  will  remain  liquid.  Pour  it  carefully  into  400  c.c.  of  cold  water 
in  a  600  c.c.  beaker.  Add  a  little  hydrochloric  acid  if  necessary  and  50 
c.c.  of  strong  sulphurous  acid,  or  5  c.c.  of  ammonium  bisulphite.  Filter 

*  Jour.  Chem.  Soc.,  xvi.  387. 


DETERMINATION  OF  COPPER.  1 85 

into  an  800  c.c.  beaker,  add  ammonia  until  a  permanent  precipitate  forms, 
redissolve  with  a  few  drops  of  hydrochloric  acid,  add  a  filtered  solution  of 
20  grammes  of  sodium  acetate  and  one-sixth  the  volume  of  the  solution 
of  acetic  acid  (1.04  sp.  gr.),  and  heat  to  boiling.  The  titanic  acid  is  precipi- 
tated almost  immediately  in  a  flocculent  condition  and  quite  free  from  iron. 
Boil  for  a  few  minutes,  allow  the  titanic  acid  to  settle,  filter,  wash  with  hot 
water  containing  a  little  acetic  acid,  dry,  ignite,  and  weigh  as  titanic  acid, 
which  contains  60  per  cent,  titanium.  Should  the  precipitate  contain  any 
appreciable  amount  of  ferric  oxide,  fuse  with  bisulphate  and  reprecipitate 
in  the  same  way. 

By  Volatilization. 

Drown  *  suggested  the  method  of  determining  titanium  by  volatilizing 
it  in  a  current  of  chlorine  gas.  The  details,  with  some  modifications, 
are  as  follows.  Treat  the  sample  exactly  as  directed  for  the  determination 
of  silicon,  by  volatilization  in  a  current  of  chlorine  gas,  page  73  et  seq. 

To  the  filtrate  from  the  silica  (page  77)  add  a  slight  excess  of  am- 
monia, acidulate  with  acetic  acid,  boil,  filter,  wash,  and  ignite  the  pre- 
cipitate. As  this  precipitate  may  contain  a  little  ferric  oxide  (carried 
over  mechanically  as  ferric  chloride),  phosphoric  acid,  tungstic  acid,  etc., 
fuse  it  with  a  little  sodium  carbonate,  dissolve  the  fused  mass  in  hot 
water,  filter,  wash,  dry,  and  ignite  the  residue,  which  will  contain  all  the 
titanic  acid  as  sodium  titanate,  and  any  iron  that  may  have  been  present 
as  ferric  oxide.  The  filtrate  will  contain  the  phosphoric  acid,  etc.  Fuse 
the  ignited  residue  with  a  little  potassium  bisulphate,  treat  it  in  the 
crucible  with  strong  sulphuric  acid,  as  directed  on  page  184,  and  deter- 
mine the  titanic  acid  in  the  manner  there  described. 


DETERMINATION    OF    COPPER. 

For  the  determination  of  copper  the  precipitate  by  hydrogen  sulphide, 
obtained  in  the  determination  of  phosphorus  (page  82),  may  be  used, 
but  in  this  case  the  precipitate  must  be  filtered  ofT  before  getting  rid  of 

*  Trans.  Inst.  Min.  Engineers,  viii.  508. 


1 86 


ANAL  YSIS  OF  IRON  AND  STEEL. 


the  excess  of  hydrogen  sulphide,  after  which,  if  any  additional  precipi- 
tate of  arsenious  sulphide  is  thrown  down  in  the  filtrate,  it  must  be 
filtered  off  before  proceeding  with  the  determination  of  phosphorus. 
Dry  and  ignite  the  filter  with  the  precipitate  of  copper  sulphide,  etc., 
in  a  porcelain  crucible,  burn  off  all  the  carbon  from  the  paper,  allow 
the  crucible  to  cool,  and  digest  the  precipitate  at  a  gentle  heat  with 
nitric  acid  and  a  few  drops  of  sulphuric  acid,  keeping  the  crucible  cov- 
ered with  a  small  watch-glass.  When  the  copper  sulphide  is  entirely 
dissolved,  remove  the  watch-glass  and  evaporate  the  solution  until  all 
the  nitric  acid  is  expelled  and  fumes  of  sulphuric  anhydride  are  given 
off.  Allow  it  to  cool,  add  enough  water  to  dissolve  all  the  cupric  sul- 
phate, heating  gently,  if  necessary,  and  wash  the  solution  into  a  plati- 
num crucible.  Place  the  crucible  in  the  little  brass  holder  (Fig.  91), 

FIG.  91. 


attach  the  weighed  platinum  cylinder,  and  connect  the  battery.  The 
battery  should  consist  of  three  Daniell's  two-quart  cells,  arranged  as  shown 
in  Fig.  92.  The  connectors  a,  b  pass  through  the  sides  of  the  box 
(which  should  be  covered),  and,  the  jars  being  connected  as  shown  in 
the  sketch,  by  simply  changing  the  wire  from  a  to  b,  three  cells  are 
brought  into  action  instead  of  two.  For  depositing  the  small  amount 
of  copper  found  in  iron  or  steel,  two  cells  furnish  a  sufficiently  strong 
current.  The  platinum  cylinder  should  weigh  about  3  or  4  grammes; 


or  THE 

UNIVERSITY 

DETERMINATION  OF  COPPER.  \ 


it  is  lowered  into  the  liquid  until  it  is  just  clear  of  the  bottom  of  the 
crucible,  and  the  crucible  is  covered  with  two  small  pieces  of  glass  to 
prevent  the  liquid  being  carried  off  by  the  escaping  gas.  It  is  much 
neater  to  deposit  the  copper  on  the  cylinder  than  in  the  crucible,  as  it 
weighs  less,  is  quite  as  easy  to  wash  and  dry,  and  there  is  no  danger 
of  any  silica  or  dirt  from  the  solution  being  covered  by  the  deposited 
copper.  When  the  copper  is  all  deposited,  usually  in  two  or  three 
hours,  remove  the  cylinder,  wash  it  with  cold  water,  then  with  alcohol, 
dry  at  100°  C,  cool,  and  weigh.  The  increase  of  weight  is  copper. 

In  pig-irons  containing  titanium  it  is  necessary  to  use  a  separate  portion 
for  the  determination  of  copper.  In  steels,  the  solution  in  the  flask  from  the 
determination  of  sulphur  (page  60)  may  be  used  for  the  determination  of 
copper.  In  this  case,  wash  the  contents  of  the  flask  into  an  800  c.c. 
beaker,  nearly  neutralize  with  ammonia,  add  5  c.c.  hydrochloric  acid,  heat 
the  solution  to  boiling,  and  pass  hydrogen  sulphide  through  the  boiling 
solution  for  fifteen  or  twenty  minutes,  filter,  wash  with  hot  water,  and  treat 
the  precipitate  as  directed  above.  In  the  case  of  pig-irons,  however,  it  is 
best  to  dissolve  in  aqua  regia,  evaporate  to  dryness,  redissolve  in  hydro- 
chloric acid,  filter,  reduce  the  iron  in  the  filtrate  with  ammonium  bisulphite, 
boil  off  the  excess  of  sulphurous  acid,  and  precipitate  by  hydrogen 
sulphide.  Instead  of  using  hydrogen  sulphide,  the  copper  may  be  precipi- 
tated in  a  sulphuric  acid  solution  by  sodium  hyposulphite.  Dissolve 
5  grammes  of  the  sample  in  a  mixture  of  150  c.c.  water  and  12  c.c.  strong 
sulphuric  acid.  Dilute  to  about  500  c-c-  with  hot  water,  heat  to  boiling, 
and  add  3  grammes  of  sodium  hyposulphite  dissolved  in  10  c.c.  hot  water. 
Boil  for  a  few  minutes,  allow  the  precipitate  to  settle,  filter,  and  wash 
with  hot  water.  Dry  the  precipitate,  which,  besides  the  cupric  sulphide, 
may  consist  of  graphite,  silica,  etc.  ;  transfer  it  to  a  small  beaker,  burn  the 
filter,  and  add  the  ash  to  the  main  portion.  Digest  the  whole  with  aqua 
regia,  dilute  with  hot  water,  filter,  wash,  add  a  few  drops  of  sulphuric 
acid,  and  evaporate  until  fumes  of  sulphuric  anhydride  are  given  off,  cool, 
dissolve  in  water,  transfer  to  the  platinum  crucible,  and  determine  the 
copper  by  the  battery  as  directed  above. 

Instead  of  determining  the  copper  by  electrolysis,  it  may  be  determined 


1 88  ANAL  YSIS  OF  IRON  AND  STEEL. 

as  cuprous  sulphide,  Cu2S,  or  as  oxide,  CuO.  To  determine  it  as  cuprous 
sulphide,  dilute  the  sulphate  obtained  by  any  of  the  methods  mentioned 
above  with  water  to  about  50  c.c.,  add  an  excess  of  ammonia,  filter  from 
ferric  oxide,  etc.,  wash  with  ammoniacal  water,  and  pass  hydrogen  sulphide 
through  the  cold  solution.  Filter,  wash  with  hydrogen  sulphide  water, 
dry  the  filter  and  precipitate,  transfer  the  latter  to  a  small  porcelain  crucible, 
burn  the  filter,  and  add  its  ash  to  the  precipitate.  Add  to  the  precipitate 
in  the  crucible  about  twice  its  volume  of  flowers  of  sulphur  and  ignite  it 
in  a  current  of  hydrogen,  as  directed  for  the  determination  of  manganese 
as  MnS,  page  112.  Weigh  as  cuprous  sulphide,  which  contains  79.82  per 
cent,  copper. 

Instead  of  igniting  the  precipitate  obtained  above  as  cuprous  sulphide, 
'the  copper  may  be  determined  as  oxide,  as  follows.  Dissolve  the  sulphide 
in  aqua  regia  in  a  small  porcelain  dish,  evaporate  nearly  dry,  dilute  with 
hot  water,  heat  to  boiling,  and  add  a  slight  excess  of  a  dilute  solution  of 
caustic  soda  or  potash.  Filter  on  a  small  ashless  filter,  wash  with  hot 
water,  dry,  transfer  the  precipitate  to  a  platinum  crucible,  burn  the  filter 
and  add  its  ash  to  the  precipitate,  moisten  the  whole  with  nitric  acid,  and 
heat  very  gently  at  first,  but  increase  the  heat  slowly  to  redness.  Cool, 
and  weigh  as  copper  oxide,  which  contains  79.85  per  cent,  copper. 


DETERMINATION    OF    NICKEL   AND    COBALT. 

The  Acetate  Method. 

Treat  3  grammes  of  the  drillings  exactly  as  directed  for  the  determina- 
tion of  manganese  by  the  acetate  method  (page  108  et  seg.).  The  precipi- 
tate by  hydrogen  sulphide  (page  1 10)  will  contain  all  the  nickel  and  cobalt 
and  a  portion  of  the  copper  contained  in  the  sample.  Filter  this  precipitate 
on  a  small  washed  filter,  wash  with  hydrogen  sulphide  water  containing 
a  little  free  acetic 'acid,  dry  and  ignite  the  filter  and  precipitate,  and  transfer 
them  to  a  small  beaker.  Dissolve  in  hydrochloric  acid  with  a  few  drops  of 
nitric  acid,  evaporate  to  dryness,  redissolve  in  from  10  to  20  drops  of  hy- 
drochloric acid,  dilute  with  hot  water  to  about  50  c.c.,  heat  the  solution  to 


DETERMINATION  OF  NICKEL  AND  COBALT.  189 

boiling,  and  pass  a  stream  of  hydrogen  sulphide  through  the  boiling 
solution  to  precipitate  any  copper  that  may  be  present.  Filter,  wash  with 
hot  water,  evaporate  the  filtrate  to  dryness,  moisten  the  dry  mass  with 
4  or  5  drops  of  hydrochloric  acid,  add  20  or  30  drops  of  cold  water  and 
then  2  or  3  grammes  of  potassium  nitrite  (KNO2)  *  dissolved  in  the  least 
possible  amount  of  water  and  acidulated  with  acetic  acid.  The  presence 
of  cobalt  is  shown  by  the  formation  of  a  bright  yellow  precipitate  of 
potassium-cobalt  nitrite,  (KNO2)6Co2(NO2)6  +  Aq.  Stir  the  solution,  and 
allow  it  to  stand  twenty-four  hours,  with  occasional  stirring.  Filter  on  a 
small  ashless  filter,  wash  with  water  containing  potassium  acetate  and  a 
little  free  acetic  acid,  remove  the  filtrate  which  contains  the  nickel,  and 
wash  the  precipitate  and  filter  free  from  potassium  acetate  with  alcohol. 
Ignite  the  filter  and  precipitate  carefully  in  a  porcelain  crucible,  being 
careful  not  to  raise  the  temperature  Jiigh  enough  to  fuse  the  precipitate; 
transfer  to  a  very  small  beaker,  and  digest  in  hydrochloric  acid  and  a  little 
potassium  chlorate.  Evaporate  to  dryness,  redissolve  in  from  3  to  5  drops  of 
hydrochloric  acid,  dilute  with  cold  water,  add  about  I  gramme  of  sodium 
acetate,  and  boil  for  an  hour  to  precipitate  the  small  amount  of  ferric  oxide 
and  alumina  that  is  always  present.  Filter,  to  the  filtrate  add  excess  of 
ammonia  and  ammonium  sulphydrate,  and  heat  to  boiling.  As  soon  as  the 
precipitate  of  cobalt  sulphide  has  settled,  filter,  wash  with  water  containing 
a  little  ammonium  sulphydrate,  dry,  and  ignite  the  precipitate  and  filter  in 
a  platinum  crucible.  When  all  the  carbon  is  burned,  allow  the  crucible 
to  cool,  pour  in  a  little  nitric  acid,  heat  carefully,  and  finally  evaporate  to 
dryness.  Add  a  few  drops  of  sulphuric  acid,  digest  until  the  sulphide  and 
oxide  are  changed  to  cobalt  sulphate,  drive  off  the  excess  of  sulphuric 
acid,  heat  finally  to  dull  redness  for  a  few  moments,  cool,  and  weigh  as 
cobalt  sulphate,  CoSO4,  which  contains  38.05  per  cent,  of  cobalt.  Heat 
the  filtrate  from  the  potassium-cobalt  nitrite  to  boiling,  add  a  slight  excess 
•of  caustic  potash,  boil  for  a  few  minutes,  filter,  and  wash  the  precipitate  of 
nickel  oxide  with  hot  water.  Dissolve  the  precipitate  on  the  filter  with 
hydrochloric  acid,  allow  the  solution  to  run  back  into  the  beaker  in  which 

*  See  page  47. 


190  A  ANALYSIS  OF  IRON  AND  STEEL. 

the  nickel  oxide  was  precipitated,  and  wash  the  filter  with  hot  water. 
Evaporate  the  solution  to  dryness,  redissolve  in  from  3  to  5  drops  of  hy- 
drochloric acid,  dilute  with  cold  water  to  about  50  c.c.,  add  I  gramme 
of  sodium  acetate,  boil  for  an  hour,  filter  off  any  ferric  oxide  and 
alumina,  and  wash  with  hot  water.  To  the  filtrate  add  an  excess  of 
ammonium  sulphydrate  (a  brown  color  shows  the  presence  of  nickel), 
acidulate  with  acetic  acid,  heat  to  boiling,  and  pass  a  current  of  hydrogen 
sulphide  through  the  boiling  solution  until  the  precipitated  sulphur  and 
nickel  sulphide  agglomerate.  Filter,  wash  with  hydrogen  sulphide  water, 
dry,  and  ignite  the  filter  and  precipitate.  Allow  the  crucible  to  cool,  add 
a  little  ammonium  carbonate  to  the  precipitate,  heat  to  dull  redness,  and 
volatilize  any  sulphuric  acid  that  may  have  been  formed  as  ammonium 
sulphate,  cool,  and  weigh  as  nickel  sulphide  or  nickel  oxide,  which  con- 
tains 78.55  per  cent,  of  nickel.  The  nickel  and  cobalt  may  also  be  weighed 
in  the  metallic  condition  by  precipitating  them  by  the  battery  from  the 
ammoniacal  solutions  of  the  sulphates.  If  it  is  not  desired  to  separate 
them,  evaporate  the  filtrate  from  the  precipitated  copper  sulphide  with  an 
excess  of  sulphuric  acid  until  the  hydrochloric  acid  is  driven  off  and  fumes 
of  sulphuric  anhydride  appear,  allow  the  beaker  to  cool,  add  about 
5  c.c.  water,  then  an  excess  of  ammonia,  filter  if  necessary,  transfer  to  a 
platinum  crucible,  and  precipitate  on  a  small  cylinder  (Fig.  91,  page  186) 
in  a  strongly  ammoniacal  solution,  using  three  cells  of  the  battery.  Wash 
the  cylinder  with  water,  then  with  alcohol,  dry  at  100°  C,  and  weigh  as 
nickel  and  cobalt.  To  determine  the  nickel  and  cobalt  separately,  precipi- 
tate the  cobalt  as  potassium-cobalt  nitrite,  treat  the  ignited  cobalt  precipi- 
tate with  an  excess  of  sulphuric  acid,  heat  until  fumes  of  sulphuric 
anhydride  are  given  off,  dilute  a  little,  make  the  solution  strongly  ammoni- 
acal, and  precipitate  the  cobalt  as  above  directed.  Precipitate  the  nickel 
oxide,  in  the  filtrate  from  the  cobalt,  by  caustic  potash  solution,  filter, 
wash,  dissolve  on  the  filter  in  hydrochloric  acid,  evaporate  the  solution 
with  sulphuric  acid,  add  excess  of  ammonia,  and  precipitate  the  nickel  by 
the  battery  as  above. 

For  the  analysis  of  nickel  steel,  which  contains  from  2  to  3  per  cent. 
of  nickel,  use   I   gramme  of  the  sample,  and,  after  obtaining  the  'precipi- 


DETERMINA  T1ON  OF  NICKEL  AND  COBAL  T.  1 9 1 

tate  of  nickel  sulphide  as  described  above,  burn  it  with  the  filter  in  a 
porcelain  crucible,  allow  it  to  cool,  add  a  little  pure  powdered  sulphur, 
and  ignite  in  a  stream  of  hydrogen  gas  as  described  on  page  112. 
Weigh  as  nickel  sulphide. 

The  Ether  Method. 

This  method  of  separation,  due  to  J.  W.  Rothe,*  is  founded  on  the 
fact  that  ether  will  take  from  an  aqueous  hydrochloric  acid  solution 
nearly  all  the  ferric  chloride,  leaving  in  the  solution  the  chlorides  of  nickel, 
cobalt,  aluminum,  chromium,  manganese,  and  copper.  The  method  was 
used  first  in  this  country  by  Mr.  George  H.  Chase,  of  the  Midvale 
Steel  Company,  and  is  given  in  considerable  detail  by  Prof.  Ad.  Carnot 
in  his  "  Methodes  d' Analyse  des  Fontes,  des  Fers,  et  des  Aciers,"  1895, 
p.  123  et  seq. 

Dissolve  from  2  f  to  5  grammes  of  the  drillings  in  a  250  c.c.  beaker 

in  aqua  regia.     Evaporate  to  dryness  to  render  silica  insoluble,  redissolve 

in    hydrochloric   acid,   dilute    slightly,  filter,  and    evaporate   the 

T^ 

filtrate  to  syrupy  consistency.  The  success  of  the  separation 
depends  largely  upon  the  specific  gravity  of  the  solution,  as  a 
solution  of  the  density  i.ioo  to  1.105  saturated  with  ether 
retains  the  smallest  amount  of  ferric  chloride.  The  tube  shown 
in  Fig.  93,  suggested  by  Carnot,  is  admirably  adapted  for  the 
treatment  with  ether.  It  consists  of  a  bulb,  B,  of  200  c.c. 
capacity,  about  20  cm.  (8  inches)  high  and  3.5  cm.  (1.5  inches) 
wide,  with  a  tube  at  either  end  3  mm.  (*/&  inch)  internal  diameter, 
carrying  the  stopcocks  A  and  C.  The  upper  one  connects 
with  a.  bulb,  D,  of  100  c.c.  capacity,  with  a  mark  at  in  to  show 
when  the  bulb  contains  30  c.c. 

Close  both  stopcocks,  pour  a  few  drops  of  ether  into  the 
upper  bulb,  open  A  to  allow  the  ether  to  run  into  B.  Close  A,  warm  the 
bulb  B  with  the  hand,  and  open  and  close  C.  This  will  create  a  partial 
vacuum  in  B.  Transfer  the  solution  from  the  beaker  to  the  bulb  D,  wash- 

*  Mittheilungen  aus  den  Koniglich  Tech.     Versuchsanstatten  zu  Berlin,  1892,  Part  iii. 

f  For  nickel  steel  containing  from  2  per  cent,  to  3  per  cent,  of  nickel  2  grammes  are  sufficient. 


192  ANAL  YSIS  OF  IRON  AND  STEEL. 

ing  it  out  of  the  beaker  with  hydrochloric  acid  of  i.i  sp.  gr.  and  filling  D 
to  the  mark  m.  This  strength  of  hydrochloric  acid  gives  the  solution, 
after  the  separation  of  the  ferric  chloride  by  ether,  a  sp.  gr.  of  i.ioo. 
Stand  the  tube  in  a  vessel  of  cold  water,  open  A  and  allow  the 
solution  to  run  into  B.  Close  A  and  fill  the  bulb  D  with  ether. 
Allow  the  ether  to  flow  slowly  into  B  so  that  it  forms  a  separate 
layer  over  the  hydrochloric  acid  solution.  Mix  the  two  liquids 
gradually  by  giving  the  apparatus  a  circular  motion,  replacing  it  in 
the  cold  water  from  time  to  time  so  as  to  avoid  a  rise  in  the  tem- 
perature, which  would  cause  a  reduction  by  the  ether  of  some  of  the 
ferric  chloride.  Finally  close  A,  shake  the  tube  well,  open  A  to 
relieve  the  pressure,  return  the  tube  to  the  water,  and  allow  it  to 
stand  some  minutes  to  give  the  liquids  the  opportunity  to  separate. 
The  upper  stratum  is  the  ethereal  solution  of  the  ferric  chloride  and 
the  lower  the  hydrochloric  acid  solution  of  the  other  metals,  with 
usually  about  I  per  cent,  of  the  ferric  chloride.  Open  the  stopcock 
C,  allow  the  lower  solution  to  run  into  a  small  beaker,  close  C,  and 
wash  the  end  of  the  tube  with  a  little  water.  Introduce  about 
10  c.c.  of  hydrochloric  acid  (i.i  sp.  gr.)  into  the  bulb  D,  allow  it 
to  run  into  B,  close  A,  shake  the  apparatus  and  allow  it  to  stand 
for  a  few  minutes.  Allow  the  lower  liquid  to  run  into  the  beaker, 
which  will  now  contain  all  the  nickel,  cobalt,  etc.,  that  were  in  the 
steel.*  One  separation  with  ether  is  generally  sufficient,  but  if  it  is 
considered  desirable  to  remove  still  more  of  the  iron,  run  the  solution 
and  washings  into  the  bulb  of  another  tube  like  the  one  described 
instead  of  into  a  beaker,  and  repeat  the  treatment  with  ether. 

Heat  the  solution  in  the  beaker  to  drive  off  the  ether  dissolved 
in  it,  add  bromine  or  a  little  hydrogen  peroxide  and  excess  of 
ammonia,  boil,  and  filter.  Redissolve  the  precipitate  and  repeat  the 
operation,  adding  the  two  filtrates  together.  The  filtrates  contain  all 
the  nickel,  cobalt,  and  copper,  while  the  insoluble  matter  contains,  be- 

*  To  recover  the  ether,  dilute  it  in  the  tube  with  an  equal  volume  of  water,  shake  the  tube  and 
allow  it  to  stand.  The  ether  rises  to  the  top  and  the  aqueous  ferric  chloride  solution  remains  below. 
Draw  off  the  latter  and  distil  the  ether  from  caustic  lime. 


DETERMINATION  OF  CHROMIUM.  193 

sides  ferric  hydrate,  any  alumina  and  chromium  sesquioxide  that  may 
have  been  in  the  steel.  Acidulate  the  filtrate  with  hydrochloric  acid, 
adding  about  5  per  cent,  of  its  volume  in  excess,  and  precipitate  the 
copper  with  hydrogen  sulphide.  Filter  and  wash.  To  the  filtrate  add 
an  excess  of  ammonia,  then  a  few  c.c.  of  ammonium  sulphydrate,  acidu- 
late with  acetic  acid,  and  pass  hydrogen  sulphide  through  the  boiling 
solution.  Filter  and  wash  the  precipitate  of  sulphur  and  nickel  and 
cobalt  sulphides.  Test  the  filtrate  by  adding  an  excess  of  ammonia, 
and  if  it  darkens  repeat  the  precipitation  with  ammonium  sulphydrate, 
acetic  acid,  and  hydrogen  sulphide.  In  the  case  of  nickel  steel,  cobalt 
is  generally  disregarded,  and  the  precipitate  is  ignited  and  weighed  after 
treatment  with  ammonium  carbonate  as  nickel  oxide,  NiO. 

Or,  heat  the  liquid  separated  from  the  ethereal  solution  to  drive 
off  the  ether,  dilute  slightly,  pass  hydrogen  sulphide  to  precipitate  the 
copper,  filter,  and  wash.  Heat  the  filtrate  to  drive  ofT  the  hydrogen 
sulphide,  add  10  c.c.  of  strong  sulphuric  acid  and  a  little  nitric  .acid, 
arid  evaporate  until  fumes  of  sulphuric  anhydride  are  given  off.  Cool, 
dilute  to  50  c.c.,  add  ammonia  in  excess,  boil,  and  filter.  Redissolve 
the  precipitate  in  dilute  sulphuric  acid,  reprecipitate,  and  filter.  Add 
the  filtrates  together  and  precipitate  on  the  battery  as  metallic  nickel. 

To  separate  the  nickel  and  cobalt,  dissolve  the  ignited  precipitate  of 
the  sulphide  obtained  above  in  hydrochloric  acid  with  a  little  nitric  acid, 
evaporate  to  very  small  bulk,  and  separate  with  potassium  nitrite  as 
described  on  page  189. 


DETERMINATION    OF    CHROMIUM. 

All  chrome  steels  are  soluble  in  hydrochloric  acid  or  in  aqua  regia, 
leaving  occasionally  a  residue  which  may  contain  small  amounts  of 
chromium.  For  gravimetric  determinations  a  preliminary  separation  of 
the  greater  part  of  the  iron  is  practically  a  necessity,  and  Rothe's 
method  for  accomplishing  this  is  unequalled  both  for  accuracy  and 
speed. 


194  ANAL  YSIS  OF  IRON  AND  STEEL. 

The  Ether  Method. 

Treat  from  I  to  5  grammes  of  the  steel  exactly  as  described  for  the 
determination  of  nickel  by  the  ether  method  (page  191),  until  the  pre- 
cipitate by  ammonia,  consisting  of  ferric  oxide,  chromium  sesquioxide, 
and  manganese  oxide,  is  obtained.  In  the  absence  of  nickel  a  single 
precipitation  is  sufficient ;  in  the  event  of  its  being  present,  two  or 
even  three  precipitations  may  be  necessary,  and  of  course  the  chromium 
and  nickel  may  be  determined  at  the  same  time.  Dry  the  precipitate, 
ignite  and  fuse  it  with  sodium  carbonate  and  a  little  sodium  nitrate. 
Extract  the  fused  mass  with  water,  filter,  and  wash  with  water  contain- 
ing a  little  sodium  carbonate.  The  filtrate  contains  the  chromium  as 
sodium  chromate,  part  of  the  alumina,  and  part  of  the  manganese.  The 
insoluble  matter  consists  of  ferric  oxide  and  the  rest  of  the  alumina 
and  manganese.  Evaporate  the  filtrate  with  an  excess  of  ammonium 
nitrate,  adding  ammonia  from  time  to  time  until  the  solution  becomes 
syrupy.  Dilute,  and  filter  from  the  alumina  and  manganese.  To  the 
filtrate,  after  boiling  off  the  ammonia,  add  an  excess  of  sulphurous  acid, 
boil  until  it  no  longer  smells  of  sulphurous  acid,  add  ammonia  in  excess, 
boil,  filter,  and  wash  the  precipitate  of  chromium  sesquioxide.  Dissolve 
in  a  little  hydrochloric  acid,  reprecipitate  with  ammonia,  filter,  wash, 
ignite,  and  weigh  as  chromium  sesquioxide,  which  contains  68.48  per 
cent,  of  chromium. 

The  Volumetric  Method. 

Galbraith  *  has  suggested  a  rapid  method  for  the  determination  of 
chromium  when  it  is  present  in  appreciable  amounts,  as  in  chrome  steel  or 
chrome  pig-iron.  Dissolve  from  I  to  3  grammes  of  the  sample  in  dilute 
sulphuric  acid  (i  part  sulphuric  acid  and  6  parts  water),  add  potassium 
permanganate  in  crystals  until  the  iron  is  all  oxidized  and  the  liquid  is 
quite  red  in  color,  then  add  as  much  more  to  oxidize  the  chromium  to 
chromic  acid.  Heat  the  solution  to  boiling,  and  boil  until  the  perman- 
ganate is  all  decomposed  and  there  remains  a  precipitate  of  manganese 

*  Chem.  News,  xxxv.  151. 


DETERMINATION  OF  CHROMIUM.  1 95 

oxide.  Filter,  wash  with  hot  water,  to  the  filtrate  add  a  measured  vol- 
ume of  standardized  ferrous  sulphate,  and  determine  the  excess  of  ferrous 
sulphate  by  a  standard  solution  of  permanganate.  From  the  amount  of 
ferrous  sulphate  oxidized  by  the  chromic  acid  calculate  the  amount  of 
chromium.  The  reaction  is  6FeSO4  +  2CrOs  +  6H2SO4  =  3Fe2(SO4)3  + 
Cr2(SO4)3  +  6H2O,  or  I  equivalent  of  chromic  acid  will  oxidize  3  equiva- 
lents of  ferrous  sulphate  to  ferric  sulphate.  Therefore,  if  the  value  of 
the  permanganate  is  known  in  metallic  iron,  and  consequently  the 
value  of  the  ferrous  sulphate  (it  being  standardized  by  the  perman- 
ganate) in  metallic  iron,  the  amount  of  chromium  is  calculated  as  fol- 
lows :  3  equiv.  Iron  =  168  :  I  equiv.  Chromium  =  52.14  ::  the  value  of 
the  ferrous  sulphate  oxidized  by  the  chromic  acid  in  iron  :  its  value  in 
chromium ;  or  multiply  the  value  of  the  ferrous  sulphate  oxidized,  in 
iron,  by  -jiV^  = -3IO3-  The  titration  is  effected  in  the  manner  directed 
for  the  determination  of  iron  in  iron  ores. 

Barba's  Modifications. 

Barba  *  has  suggested  several  modifications  which  decidedly  improve 
the  method.  To  avoid  the  large  precipitate  of  manganese  dioxide,  he 
uses  nitric  acid  to  oxidize  the  iron,  having  found  that  even  a  consider- 
able excess  of  this  reagent  does  not  affect  the  subsequent  reactions. 
He  uses,  most  successfully,  ammonia  to  destroy  the  excess  of  potassium 
permanganate.  The  method  is  as  follows : 

Dissolve  1.25  grammes  steel  in  20  c.c.  sulphuric  acid  (1.2  sp.  gr.). 
When  solution  is  complete,  add  nitric  acid  drop  by  drop  until  the  iron 
is  oxidized;  5  c.c.  of  nitric  acid  (1.2  sp.  gr.)  is  generally  sufficient. 

Boil  to  remove  nitrous  fumes,  and  add  hot  water  to  bring  the  volume 
to  150  c.c. ;  add  from  a  pipette  5  c.c.  of  a  saturated  solution  of  potas- 
sium permanganate  and  boil  briskly  for  from  fifteen  to  twenty  minutes; 
remove  from  the  plate,  wash  down  the  sides  of  the  beaker  to  remove  all 
permanganate,  and  add  25  c.c.  strong  ammonia  down  the  side  of  the 
beaker;  shake  well,  and  replace  on  the  cooler  part  of  the  plate  to  avoid 

*  The  Iron  Age,  lii.  153. 


196  ANALYSIS  OF  IRON  AND  STEEL. 

"  bumping,"  of  which  there  is  some  danger  if  the  heat  be  raised  too 
rapidly.  Shake  occasionally  and  digest  for  about  fifteen  minutes,  or  until 
the  permanganate  is  all  decomposed,  then  add  cautiously  20  c.c.  dilute 
sulphuric  acid  (1.58  sp.  gr.)  and  bring  gently  to  boiling.  Cool  the  solution 
and  pour  into  a  graduated  250  c.c.  flask.  Make  up  to  mark  with  cold 
water,  and  mix  well  by  pouring  back  and  forth  into  a  dry  beaker  a  few 
times.  Allow  the  precipitate  to  settle,  and  filter  through  superposed  fun- 
nels, with  close,  hard,  dry  filters,  into  a  dry  beaker ;  measure  off  200  c.c. 
(equal  to  I  gramme  sample)  of  the  clear  filtrate,  titrate  by  adding  a  known 
excess  of  ferrous  sulphate,  and  determine  the  excess  by  standard  per- 
manganate. 


DETERMINATION    OF    ALUMINUM. 

Stead's  Method.* 

Weigh  6,  12,  or  24  grammes  steel,  place  in  a  600  c.c.  beaker,  cover 
with  a  watch-glass,  dissolve  in  hydrochloric  acid  (strong),  evaporate  to 
dryness,  redissolve  in  hydrochloric  acid,  filter  into  a  1000  c.c.  beaker 
through  an  ashless  filter,  nearly  neutralize  the  filtrate  with  dilute  am- 
monia, and  boil.  The  filtrate  should  measure  500  or  600  c.c.  Add  to 
the  solution  I  or  2  c.c.  of  saturated  solution  of  ammonium  phosphate, 
and  then  a  large  excess  of  sodium  hyposulphite,  boil  till  all  sulphurous 
acid  has  passed  off  (half  an  hour's  boiling  should  be  sufficient);  just 
before  filtering  add  20  c.c.  of  a  saturated  solution  of  ammonium  acetate, 
stir  to  mix,  and  filter  through  an  ashless  filter,  wash  precipitate  and  filter 
five  or  six  times,  add  to  the  beaker  in  which  the  precipitate  had  been 
formed  10  c.c.  hydrochloric  acid,  heat  to  boiling,  remove  the  vessel  contain- 
ing the  filtrate,  and  instead  of  it  place  under  the  funnel  a  platinum  dish,  and 
pour  over  the  filter  the  boiling  acid.  Rinse  out  the  beaker  and  wash  all 
soluble  matter  on  the  filter  with  a  fine  jet,  evaporate  the  solution  to  dry- 
ness  in  the  platinum  dish,  and  heat  to  a  temperature  of  300°  or  400°  F. 
on  the  hot  plate  to  drive  off  excess  of  acid. 

*  Prepared  by  Mr.  J.  E.  Stead,  of  Middlesboro' ,  England,  for  this  volume. 


DETERMINATION  OF  ALUMINUM.  197 

Add  from  2  to  5  grammes  pure  sodium  hydrate  made  from  sodium 
free  from  aluminum  and  about  2  c.c.  water.  Heat  gently  over  a  rose-burner 
for  ten  minutes,  maintaining  the  mass  in  a  fluid  state  all  the  time.  Cool 
and  add  water,  and  boil  till  solution  is  complete.  Make  the  bulk  of  the 
solution  to  300  c.c.  and  note  the  temperature  exactly.  Shake  well  and 
filter  through  an  ashless  filter.  Measure  off  250  c.c.  at  the  original  tem- 
perature, equal  to  5,  10,  or  20  grammes  steel.  If  any  yellow  tint  is 
observable  chromium  may  be  present.  In  this  case  the  aluminum  phos- 
phate must  be  neutralized  with  hydrochloric  acid  and  precipitated  by 
ammonium  carbonate,  taking  care  to  boil  the  solution  well  to  free  from 
excess  of  ammonia  before  filtering.  Filter  through  an  ashless  filter,  dry, 
burn,  and  weigh,  dissolve  the  precipitate  in  hydrochloric  acid  and  deter- 
mine phosphoric  acid  in  it,  and  deduct  the  weight  found  from  the  weight 
of  the  original  precipitate.  If  chromium  is  absent,  neutralize  the  solution 
with  hydrochloric  acid  as  before  described,  boil  and  add  excess  of 
sodium  hyposulphite,  and  boil  for  half  an  hour,  filter  off  the  precipitate, 
burn,  and  weigh  as  pure  aluminum  phosphate,  which  contains  22.18  per 
cent,  of  aluminum. 

Carnot's  Method.* 

M.  Carnot  states  that  the  method  is  very  similar  to  that  published 
by  Mr.  J.  E.  Stead  in  the  Journal  of  the  Society  of  Chemical  Industry, 
1889,  page  965,  but  that  he  had  used  and  taught  it  in  the  Ecole  des 
Mines  for  eight  years.  It  is  founded  on  the  reaction  that  he  pointed  out 
in  1 88 1,  that  aluminum  is  precipitated  as  the  neutral  phosphate  from  a 
boiling  solution  faintly  acid  with  acetic  acid.  The  precipitation  succeeds 
equally  well  when  the  solution  contains  iron,  if  the  ferric  salt  has  been 
previously  reduced  to  ferrous  by  sodium  hyposulphite. 

Treat  10  grammes  of  the  iron  or  steel  in  a  platinum  dish  covered 
with  a  piece  of  platinum-foil  with  hydrochloric  acid,  and  when  solution 
is  complete,  dilute  and  filter  into  a  flask,  washing  the  carbon,  silica,  etc., 
on  the  filter  thoroughly  with  distilled  water.  Neutralize  the  solution 
with  ammonia  and  sodium  carbonate,  but  see  that  no  permanent  precipi- 

*  A.  Carnot,  Moniteur  Scientifique,  1891,  p.  14. 


Ip8  ANALYSIS  OF  IRON  AND  STEEL. 

tate  is  formed,  then  add  a  little  sodium  hyposulphite,  and,  when  the 
liquid — at  first  violet — becomes  colorless,  2  or  3  c.c.  of  a  saturated  solution 
of  sodium  phosphate  and  5  or  6  grammes  of  sodium  acetate  dissolved 
in  a  little  water.  Boil  the  solution  about  three-quarters  of  an  hour,  or 
until  it  no  longer  smells  of  sulphurous  acid.  Filter,  and  wash  the  pre- 
cipitate of  aluminum  phosphate,  mixed  with  a  little  silica  and  ferric 
phosphate,  with  boiling  water.  Treat  the  precipitate  on  the  filter  with 
hot  dilute  hydrochloric  acid,  allow  the  solution  to  run  into  a  platinum 
dish,  evaporate  to  dryness,  and  heat  at  100°  C.  for  an  hour  to  render  the 
silica  insoluble.  Dissolve  in  hot  dilute  hydrochloric  acid,  filter  from  the 
silica,  dilute  to  about  100  c.c.  with  cold  water,  neutralize  as  before,  add  a 
little  hyposulphite  in  the  cold,  then  a  mixture  of  2  grammes  of  sodium 
hyposulphite  and  2  grammes  of  sodium  acetate,  boil  for  one-half  hour, 
wash,  and  weigh  as  aluminum  phosphate,  which  contains  22.18  per  cent, 
of  aluminum. 

Ether  Method. 

Treat  5  grammes  of  steel  as  described  for  the  determination  of  nickel 
and  evaporate  the  hydrochloric  acid  solution,  which  may  contain  nickel, 
chromium,  copper,  etc.,  until  the  ether  is  driven  off,  add  a  few  drops  of 
nitric  acid  or  bromine  to  oxidize  the  iron,  and  precipitate  by  ammonia. 
Boil  for  a  few  minutes,  filter,  and  wash ;  redissolve  in  hydrochloric  acid, 
and  reprecipitate,  filter,  and  wash  with  boiling  water.  The  precipitate  will 
contain  only  iron,  aluminum,  and  chromium.  When  chromium  is  absent, 
dissolve  the  precipitate  in  hydrochloric  acid,  evaporate  to  dryness,  dis- 
solve in  a  few  drops  of  hydrochloric  acid,  filter,  and  dilute  with  cold 
water  to  100  c.c.,  add  2  or  3  c.c.  of  sodium  phosphate,  and  proceed  as  in 
the  second  precipitation  of  aluminum  phosphate  by  Carnot's  method. 

When  chromium  is  present,  fuse  the  precipitate  of  ferric  oxide,  alu- 
mina, and  chromic  oxide  with  sodium  carbonate  and  a  little  sodium  nitrate, 
dissolve  in  water,  add  ammonium  nitrate,  boil  well,  and  filter.  The 
chromic  acid  will  be  in  the  filtrate  and  the  ferric  oxide  and  alumina  will 
be  insoluble.  Dissolve  in  hydrochloric  acid  and  proceed  as  when 
chromium  is  absent. 


DETERMINATION  OF  ARSENIC. 


I99 


FIG,  94. 


DETERMINATION    OF    ARSENIC. 
By  Distillation. 

Lundin  *  has  suggested  the  following  method  of  determining  arsenic, 
which  gives  very  good  results.  Dissolve  10  grammes  of  drillings  in  a 
large  beaker  in  nitric  acid  (1.2  sp.  gr.),  transfer  the  solution  to  a  plati- 
num or  porcelain  dish,  add  25  c.c.  sulphuric  acid,  and  evaporate  until 

copious  fumes  of  sulphuric  acid  are 
given  off.  Cool  the  dish,  add  50  c.c. 
of  water,  and  evaporate  again  until  the 
excess  of  sulphuric  acid  is  driven  off, 
and  the  ferric  sulphate  is  so  dry  that  it 
can  readily  be  transferred  to  a  flask  of 
about  500  c.c.  capacity.  Add  to  the 
mass  in  the  flask  15  grammes  finely 
powdered  ferrous  sulphate,  pour  in  150 
c.c.  strong  hydrochloric  acid,  and  close 
the  flask  with  a  stopper  carrying  a  tube 
bent  twice  at  right  angles  and  connected 
by  a  rubber  tube  with  a  50  c.c.  pipette, 
the  point  of  which  dips  about  y2  inch 
(12  mm.)  into  300  c.c.  of  water  in  a  beaker,  as  shown  in  Fig.  94.  Heat  the 
liquid  in  the  flask  gradually  until  it  boils,  and  continue  the  distillation  until 
the  wide  part  of  the  pipette  becomes  heated.  The  arsenic  acid  in  the 
solution  is  reduced  by  the  ferrous  sulphate,  and,  in  the  strong  hydrochloric 
acid  solution,  is  distilled  over  as  arsenious  chloride.  Remove  the  light, 
disconnect  the  pipette,  heat  the  solution  in  the  beaker  to  about  70°  C, 
and  pass  a  rapid  current  of  hydrogen  sulphide  through  it  until  it  is  com- 
pletely saturated.  Remove  the  excess  of  hydrogen  sulphide  by  a  current 
of  carbonic  acid,  and  when  the  solution  smells  very  faintly  of  hydrogen 
sulphide,  filter  off  the  yellow  precipitate  of  arsenious  sulphide  on  a  Gooch 


Jern-Kontorets  Annaler,  1883,  p.  360;  Chem.  News,  li.  115. 


200  ANAL  YSIS  OF  IRON  AND  STEEL. 

crucible  or  on  a  counterpoised  filter,*  wash  with  water,  then  with  alcohol, 
then  with  pure  carbon  disulphide,  dry  at  100°  C,  and  weigh  as  arsenious 
sulphide,  which  contains  60.93  per  cent  of  arsenic. 

Or,  after  filtering  the  precipitate  on  the  felt  in  a  Gooch  crucible,  trans- 
fer the  precipitate  and  felt  to  a  small  beaker,  add  a  little  fuming  nitric 
acid,  and,  when  action  has  nearly  ceased,  heat  gently  until  the  sulphur  is 
dissolved,  dilute,  filter,  and  evaporate  to  about  10  c.c.  Add  5  c.c.  of  mag- 
nesia-mixture and  then  ammonia  equal  to  one-half  the  volume  of  the 
solution.  Stir  the  solution  vigorously  from  time  to  time,  keeping  it  cool 
by  immersing  the  beaker  in  ice-water,  and  allow  it  to  stand  twelve  hours. 
Filter  on  a  Gooch  crucible,  wash  the  precipitate  of  ammonium-magnesium 
arsenate  with  the  ammonia-water  containing  ammonium  nitrate,  used  for 
washing  the  ammonium-magnesium  phosphate  (page  85),  dry  at  103°  C. 
for  half  an  hour,  then  increase  the  heat  very  gradually  to  redness,  and 
ignite  strongly  for  a  few  minutes.  Weigh  as  magnesium  arsenate,  which 
contains  48.30  per  cent,  of  arsenic. 


DETERMINATION    OF    TIN. 

Tin  is  a  most  unusual  constituent  of  steel  or  iron,  but  has  been  found 
in  the  former  in  cases  where  scrap  from  tinned  iron,  from  which  the  tin 
has  been  removed  by  a  chemical  process,  has  been  melted  in  the  open- 
hearth  furnace  as  a  portion  of  the  charge.  Dissolve  10  grammes  of  the 
sample  in  hydrochloric  acid,  dilute  to  600  c.c.,  and  saturate  the  solution 
with  hydrogen  sulphide.  Allow  it  to  stand  for  several  hours,  filter,  and 
wash  with  water  containing  hydrogen  sulphide.  Treat  the  precipitate  on 
the  filter  with  ammonium  sulphydrate,  allowing  the  solution  and  washings 
to  run  into  a  250  c.c.  beaker.  Acidulate  with  acetic  acid,  allow  to  stand 
in  a  warm  place  for  several  hours,  filter,  and  wash  with  water  containing 
ammonium  acetate  made  slightly  acid  with  acetic  acid.  Dry  the  precipi- 
tate and  filter,  transfer  the  precipitate  to  a  weighed  porcelain  crucible,  burn 

*  See  page  28. 


DETERMINATION  OF  TUNGSTEN.  2OI 

the  filter  and  add  its  ash  to  the  precipitate,  add  a  little  sulphur,  and  ignite 
in  a  current  of  hydrogen  sulphide,  as  directed  for  the  determination  of 
manganese  as  sulphide  (page  112).  Any  arsenic  present  will  be  volatilized, 
but  it  is  not  possible  to  weigh  the  tin  as  sulphide,  as  its  composition  is  not 
constant.  Heat  the  crucible  carefully,  and  roast  the  precipitate  with  access 
of  air,  heat  it  strongly  two  or  three  times  with  ammonium  carbonate  to 
volatilize  any  sulphuric  acid  that  may  have  been  formed,  cool,  and  weigh 
as  stannic  oxide,  which  contains  78.81  per  cent,  of  tin. 


DETERMINATION    OF    TUNGSTEN. 

Dissolve  from  I  to  10  grammes  of  the  drillings  in  nitric  acid  (1.2  sp. 
gr.),  evaporate  to  dryness  in  the  air-bath,  redissolve  in  hydrochloric  acid,. 
dilute  slightly,  and  boil  for  some  time.  The  tungstic  acid  is  deposited  as 
a  yellowish  powder.  Dilute,  filter,  wash  with  hot  water  containing  a 
little  hydrochloric  acid,  ai\d  finally  with  alcohol  and  water.  The  precipi- 
tate consists  of  tungstic  acid  mixed  with  more  or  less  silica,  graphite,  and 
perhaps  a  little  ferric  oxide,  titanic  acid,  etc.  Dry  and  ignite  the  filter  and 
precipitate,  and  burn  off  the  carbon.  Allow  the  crucible  to  cool,  moisten 
the  precipitate  with  water,  add  a  little  sulphuric  acid  and  an  excess  of 
hydrofluoric  acid.  Evaporate  to  dryness  under  a  hood,  and  ignite  to 
drive  off  the  sulphuric  acid.  Fuse  the  residue  with  five  times  its  weight  of 
sodium  carbonate,  allow  it  to  cool,  dissolve  in  water,  filter  from  any- 
insoluble  matter,  and  wash  with  water  containing  a  little  sodium  carbonate. 
The  filtrate  contains  all  the  tungsten,  as  sodium  tungstate.  Nearly 
neutralize  with  nitric  acid,  and  boil  off  the  carbonic  acid,  allow  the  solu- 
tion to  cool  slightly,  and  add  a  faint  but  distinct  excess  of  nitric  acid. 
Add  an  excess  of  mercurous  nitrate,*  and  then  mercuric  oxide  diffused  in 
water,*  until  the  free  acid  is  all  neutralized.  The  tungsten  is  all  precipi- 
tated as  mercurous  tungstate,  and  can  be  washed  perfectly  free  from 

*  See  page  56. 


202  ANAL  YSIS  OF  IRON  AND  STEEL. 

sodium  salts  with  hot  water.  Allow  the  precipitate  to  settle,  filter  on  an 
ashless  filter,  wash  with  hot  water,  and  dry  the  filter  and  precipitate. 
Separate  the  precipitate  from  the  filter,  burn  the  filter  in  a  platinum  crucible, 
add  the  precipitate,  and  heat  it  under  a  hood  with  a  good  draft,  increasing 
the  heat  gradually  to  a  bright  red.  The  mercury  volatilizes,  and  there 
remains  only  tungstic  acid.  Cool,  and  weigh  as  tungstic  acid,  which 

contains  79.31  per  cent,  of  tungsten. 

i 

Rapid  Method  for  Tungsten. 

A  rapid  method  for  the  determination  of  tungsten  in  high  tungsten 
steels  and  one  that  gives  results  sufficiently  accurate  for  ordinary  work 
is  as  follows : 

Treat  I  gramme  of  the  steel  in  a  No.  3  Griffin's  beaker  with 
25  c.c.  of  aqua  regia,  evaporate  to  dryness,  redissolve  in  10  c.c.  strong 
hydrochloric  acid,  add  I  or  2  c.c.  strong  nitric  acid,  heat  for  a  few 
minutes,  dilute  with  hot  water  to  100  c.c.,  and  boil  for  ten  minutes. 
Filter,  wash  with  water  containing  a  little  hydrochloric  acid,  and  ignite. 
Treat  the  precipitate  in  the  crucible  with  a  few  drops  of  sulphuric  acid 
and  some  hydrofluoric  acid,  evaporate  to  dryness,  ignite,  and  weigh. 
Fuse  the  precipitate  with  a  little  sodium  carbonate,  dissolve  in  hot 
water,  filter  off  the  ferric  oxide,  wash  it  well  with  hot  water,  return 
it  to  the  crucible,  ignite,  and  weigh.  The  difference  between  the  two 
weights  is  tungstic  acid. 


DETERMINATION    OF    VANADIUM. 

Vanadium  is  occasionally  found  in  pig-iron,  and  may  be  determined 
with  great  accuracy  by  the  following  method.  Treat  5  grammes  of 
the  drillings  with  50  c.c.  nitric  acid  (1.2  sp.  gr.)  in  a  No.  4  beaker. 
When  all  action  has  ceased,  transfer  the  liquid  to  a  porcelain  dish, 
evaporate  to  dryness,  and  heat  at  a  gradually  increasing  temperature 
over  a  Bunsen  burner  until  the  nitrates  are  nearly  all  decomposed 


DETERMINATION  OF  VANADIUM.  203 

and  the  mass  separates  easily  from  the  bottom  and  sides  of  the  dish. 
Transfer  the  cooled  mass  to  a  porcelain  or  agate  mortar,  and  grind 
it  thoroughly  with  30  grammes  of  dry  sodium  carbonate  and  3 
grammes  of  sodium  nitrate.  Transfer  to  a  large  platinum  crucible, 
and  fuse  well  for  about  an  hour  at  a  high  temperature.  Run  the 
fused  mass  well  up  on  the  sides  of  the  crucible,  allow  it  to  cool, 
dissolve  in  hot  water,  and  filter.  Dilute  the  filtrate  to  about  600  c.c., 
and  add  nitric  acid  carefully  to  get  rid  of  the  carbonic  acici.  Boil 
off  the  latter,  but  be  careful  to  keep  the  solution  always  slightly 
alkaline.  Filter,  and  to  the  filtrate  add  a  few  drops  of  nitric  acid  to 
make  it  faintly  acid,  when  the  appearance  of  a  yellowish  coloration 
is  an  indication  of  the  presence  of  vanadic  acid.  Add  to  the  solution 
a  few  c.c.  of  mercurous  nitrate,*  and  then  an  excess  of  mercuric 
oxide  in  water,*  to  render  the  solution  neutral  f  and  insure  the 
complete  precipitation  of  all  the  mercurous  vanadate.  With  the  mer- 
curous vanadate  are  precipitated  also  all  the  phosphoric,  chromic, 
tungstic,  and  molybdic  acids  as  mercurous  salts.  Heat  to  boiling, 
filter,  and  wash  the  precipitate.  Dry  it,  separate  the  paper,  burn  it 
in  a  platinum  crucible,  add  the  precipitate,  heat  carefully  to  expel 
the  mercury,  and  finally  heat  to  full  redness.  Fuse  the  brownish-red 
mass  remaining  in  the  crucible  with  a  little  sodium  carbonate  and  a  pinch 
of  sodium  nitrate,  dissolve  the  cooled  mass  in  water,  and  filter  into  a  small 
beaker.  Add  to  the  solution  pure  ammonium  chloride  in  excess  (about 
3.5  grammes  to  each  10  c.c.  of  solution),  and  allow  it  to  stand  for  some 
time,  stirring  occasionally.  Ammonium  vanadate,  insoluble  in  a  saturated 
solution  of  ammonium  chloride,  separates  out  as  a  white  powder.  It  is 
necessary  to  keep  the  solution  decidedly  alkaline,  and  a  drop  or  two  of 
ammonia  must  be  added  from  time  to  time.  The  appearance  of  the 
faintest  yellowish  tint  to  the  solution  is  evidence  that  it  has  become 
slightly  acid,  and  this  must  be  corrected  or  the  result  will  be  too  low. 
Filter  on  a  small  ashless  filter,  wash  first  with  a  saturated  solution  of 
ammonium  chloride  containing  a  drop  or  two  of  ammonia,  and  then 


*  See  page  56.  f  Am.   Chem.  Jour.,  v.  373. 


204  ANALYSIS  OF  IRON  AND  STEEL. 

with    alcohol.     Dry,    ignite,    moisten  with  a  drop  or  two   of  nitric  acid, 
ignite,  and  weigh   as    vanadic   acid,    which    contains    56.22    per    cent,    of 

vanadium. 

« 

RAPID  METHOD  FOR  VANADIUM. 

In  the  absence  of  chromium,  the  method  of  Campagne  is  simple  and 
accurate.  (Comptes-Rendus,  1903,  vol.  cxxxvii.  p.  570.) 

Treat  from  I  to  5  grammes  by  the  ether  method  as  described  on  page  191. 
The  aqueous  solution  contains  the  vanadium,  chromium,  aluminum,  man- 
ganese, copper,  nickel,  and  cobalt,  with  a  little  iron.  Evaporate  this  solution 
to  dryness  several  times  with  a  large  excess  of  hydrochloric  acid  and 
reduce  the  vanadic  acid  to  di-vanadyl  chloride,  according  to  the  equation, 
V2O5+6HC1=2VOC12+3H2O+C12.  Add  5  c.c.  of  strong  sulphuric  acid 
and  evaporate  until  all  the  hydrochloric  acid  is  expelled  and  fumes  of 
sulphuric  acid  appear.  By  this  operation  di-vanadyl  sulphate  is  formed  : 

2VOC12  +  2H2SO  - V202  (S04)2  +  4HC1. 

Allow  it  to  cool  and  dilute  to  200  or  300  c.c.     Warm  to  about  60°  C.  and 
titrate  with  permanganate  solution. 

5V2O2(SO4)2  +  2KMnO4  +  8H2SO4  =--  5V2O2(SO4)3  +  K2SO4  + 
2MnSO4-f  8H2O.  Now,as  ioFeSO4  +  2KMnO4  -f  8H2SO4=5Fe2(SO4)3  + 
K2SO4  +  2MnSO4  -f  8H2O,  then  loV  =  5 12  is  equal  to  icFe  =  550,  or 

Vanadium  =  .9i43Fe. 

The  vanadium  equals  the  value  of  the  permanganate  solution  in  iron  multi- 
plied by  .9143. 

Small  amounts  of  ferric  salts  do  not  interfere  with  the  reaction,  but  when 
chromium  is  present  to  the  extent  of  2  per  cent,  or  over,  the  color  of  the 
chrome  salt  masks  the  end  reaction.  The  color  of  the  di-vanadyl  sulphate 
is  pale  blue,  while  that  of  the  chromium  sulphate  is  green.  It  is,  there- 
fore, impossible  to  tell  from  the  color  of  the  solution  under  the  conditions 
whether  the  sample  contains  vanadium  or  not,  the  discoloration  of  the  per- 
manganate solution  being  the  only  indication  of  its  presence. 

In  Ferro- Vanadium. 
The  method  is  exactly  the  same  as  in  steels,  but  it  is  necessary  to  take 


DETERMINATION  OF  MOLYBDENUM.  2O5 

only  from  .5  to  I  gramme  of  the  material.     In  material  containing  over  40 
per  cent,  of  vanadium  the  ether  separation  is  unnecessary. 


DETERMINATION  OF  MOLYBDENUM. 

In  irons  and  steels  containing  from  I  to  10  per  cent,  of  molyb- 
denum treat  I  gramme  of  the  drillings  in  a  beaker  with  from  50  c.c. 
to  100  c.c.  nitric  acid  (1.2  sp.  gr.),  and  heat  on  hot  plate  until  all  action 
has  ceased,  evaporate  to  dry  ness  in  an  air-bath,  take  up  with  hydro- 
chloric acid  and  heat  until  all  ferric  oxide  is  dissolved,  evaporate  to 
dryness,  take  up  with  dilute  hydrochloric  acid  and  filter  from  silica; 
treat  this  residue  with  sulphuric  and  hydrofluoric  acids,  weighing  if 
silicon  is  to  be  determined,  and  after  weighing  the  second  time  fuse 
the  residue  with  sodium  carbonate  and  a  little  sodium  nitrate,  dissolve 
in  water,  filter,  and  add  filtrate  to  the  main  solution.  Reduce  the  ferric 
chloride  with  ammonium  bisulphite  as  in  the  determination  of  phosphorus 
(page  8 1  et  seq),  and  after  having  driven  off  the  sulphurous  acid,  pass 
hydrogen  sulphide  gas  into  the  solution  for  an  hour,  keeping  it  at  about 
80°  C.  At  the  end  of  this  time  make  the  solution  ammoniacal,  then 
acidulate  with  hydrochloric  acid  and  pass  hydrogen  sulphide  again  for  a 
few  minutes ;  stand  the  beaker  aside  and  allow  the  precipitate  to  settle 
until  the  supernatant  liquid  is  clear,  filter  on  paper,  and  wash  with  hydro- 
gen sulphide  water.  Treat  the  .filtrate  again  in  the  same  way,  and  if  any 
precipitate  forms,  filter  on  another  paper.  Wash  the  precipitates  from  the 
papers  into  a  beaker  with  hot  ammonium  sulphide  solution,  burn  the 
papers  in  a  porcelain  crucible,  cover  the  residue  in  the  crucible  with 
flowers  of  sulphur  and  heat  gently  until  the  sulphur  is  melted,  then  add  a 
little  sodium  carbonate,  cover  the  crucible  with  a  lid  and  heat  until  liquid ; 
cool,  dissolve  in  hot  water,  filter,  and  add  the  filtrate  to  the  main  solution. 
Warm  the  sulphide  solution  for  an  hour  or  so  and  filter,  washing  with 
ammonium  sulphide  water  from  any  sulphides  that  may  be  insoluble  in 
the  ammonium  sulphide,  but  which  should  be  soluble  in  hydrochloric  acid, 
unless  some  copper  has  dissolved  in  the  previous  treatment ;  otherwise 
the  treatment  with  ammonium  sulphide  has  been  insufficient. 


206  ANAL  YSIS   OF  IRON  AND   STEEL. 

Heat  the  filtrate,  which  should  be  yellow  in  color,  almost  to  boiling, 
and  acidulate  carefully  with  hydrochloric  acid ;  when  the  acid  is  in  excess, 
all  the  molybdenum  sulphide  will  be  precipitated,  but  hydrogen  sulphide 
may  be  passed  for  a  short  time  if  necessary.  Heat  the  solution  gently 
until  all  smell  of  hydrogen  sulphide  is  driven  off,  and  filter  on  a  weighed 
Gooch  crucible,  washing  with  hot  water.  Dry  at  100°  or  120°  C.  and 
ignite  in  a  stream  of  hydrogen,  until  weight  is  constant,  by  placing  the 
bowl  of  a  clay  tobacco-pipe  in  the  crucible  and  passing  the  hydrogen  into 
the  stem.  The  hydrogen  gas  must  have  replaced  the  air  in  the  pipe  and 
crucible  before  the  heat  is  applied.  Heat  to  dull  redness  for  one  hour, 
remove  the  heat,  and  allow  to  cool  with  the  hydrogen  passing.  Weigh, 
and  repeat  the  ignition ;  the  second  weight  will  rarely  differ  much  from  the 
first.  The  precipitate  is  molybdenum  disulphide,  which  contains  60  per 
cent,  of  molybdenum. 

In  Ferro-Molybdenum. 

In  ferro  high  in  molybdenum  treat  .2  gramme  in  a  large  platinum 
crucible  with  nitric  acid  (1.2  sp.  gr.)  until  action  has  ceased;  evaporate  to 
dryness  and  gently  ignite,  fuse  with  from  20  to  30  grammes  sodium  car- 
bonate and  3  grammes  sodium  nitrate,  dissolve  in  water,  filter,  again  fuse 
the  residue,  dissolve,  and  filter,  add  together  the  two  filtrates,  acidulate  with 
hydrochloric  acid,  boil  to  expel  carbonic  acid,  and  pass  hydrogen  sulphide 
to  precipitate  the  molybdenum  sulphide.  From  this  point  proceed  as  in 
iron  and  steel. 

RAPID    METHODS.* 

Treat  .5  gramme  of  the  sample  in  a  large  platinum  crucible  with  2  c.c. 
sulphuric  acid  and  12  c.c.  water  until  dissolved,  evaporate  to  dryness,  add 
30  grammes  fused  potassium  bisulphate,  and  fuse  thoroughly.  Run  the 
fused  mass  well  up  on  the  sides  of  the  crucible  and  cool.  Place  the 
crucible  in  a  beaker  with  about  500  c.c.  of  hot  water  and  heat  until  the 
fused  mass  has  dissolved.  Wash  and  remove  the  crucible. 

Cool  the  solution,  transfer  to  a  litre  flask,  add  100  c.c.  ammonium 
hydrate,  and  when  the  solution  has  the  temperature  of  the  air  dilute  to 

*  See  F.  T.  Kopp  in  Journal  of  American  Chemical  Society,  xxiv.  1 86. 


DETERMINATION  OF  NITROGEN.  2O/ 

the  mark.  Mix  thoroughly  by  passing  the  solution  into  a  dry  beaker  and 
back  into  the  flask  several  times.  Allow  the  precipitate  of  ferric  oxide  to 
settle  and  filter  through  a  dry  paper.  To  500  c.c.  of  the  clear  filtrate  add 
40  c.c.  strong  sulphuriq  acid,  pass  through  a  reductor,  and  titrate  exactly 
as  described  on  page  93  et  seq.  To  calculate  the  amount  of  molybdenum, 
multiply  the  value  of  I  c.c.  of  the  permanganate  solution  in  iron  by  .58709, 
which  is  the  ratio  of  iron  to  molybdenum.  This  will  give  the  value 
of  I  c.c.  of  the  permanganate  in  molybdenum.  As  .25  gramme  is  used, 
multiply  the  number  of  c.c.  required  by  4  and  the  result  by  the  value  of 
the  permanganate  solution  in  molybdenum,  and  the  result  is  the  amount 
of  molybdenum  in  one  gramme  of  the  sample. 

When  tungsten  is  present,  treat  I  gramme  as  on  page  201,  but  before 
filtering  off  the  tungstic  acid  dilute  to  100  c.c.,  filter  through  a  dry  filter, 
evaporate  50  c.c.  of  the  filtrate  in  a  crucible  with  the  addition  of  10  c.c. 
sulphuric  acid,  fuse  with  potassium  bisulphate,  and  proceed  as  above, 
calculating  the  amount  to  .5  gramme. 

In  Ferro-Molybdenum. 

Dissolve  .5  gramme  of  the  sample  in  a  platinum  crucible  in  dilute 
nitric  acid,  add  2  c.c.  strong  sulphuric  acid,  evaporate  to  dryness,  fuse 
with  potassium  bisulphate,  and  proceed  as  above. 


DETERMINATION    OF    NITROGEN. 

This  method  is  based  on  the  reaction  by  which  the  nitrogen  in 
iron  or  steel  is  converted  into  ammonia  by  hydrochloric  acid  during 
the  solution  of  the  steel  in  this  reagent. 

It  was  first  published  by  A.  H.  Allen,*  with  many  interesting  details  and 
results.  The  modifications  of  the  method  as  described  by  Mr.  Allen  are  by 
Prof.  J.  W.  Langley,f  of  Pittsburg,  and  consist  essentially  in  the  use  of  caustic 
soda  freed  from  nitrates  and  nitrites  by  the  copper-zinc  couple  and  subse- 
quent distillation  of  all  ammonia  formed,  and  in  a  few  details  of  manipulation. 

The  reagents  required  are : 

Hydrochloric   Acid  of  i.i   sp.  gr.,  free  from   Ammonia,    which    may 

*  Chemical  News,  xli.  231.  f  Communicated  to  the  author. 


208  ANAL  YSIS   OF  IRON  AND   STEEL. 

be  prepared  by  distilling  pure  hydrochloric  acid  gas  into  distilled 
water  free  from  ammonia.  To  do  this,  take  a  large  flask  fitted  with 
a  rubber  stopper  carrying  a  separatory  funnel-tube  and  an  evolution-tube, 
fill  it  half  full  of  strong  hydrochloric  acid,  connect  the  evolution-tube 
with  a  wash-bottle  connected  with  a  bottle  containing  the  distilled 
water.  Admit  strong  sulphuric  acid  free  from  nitrous  acid  to  the 
flask  through  the  funnel-tube,  apply  heat  as  required,  and  distil  the 
gas  into  the  prepared  water. 

Test  the  acid  by  admitting  some  of  it  into  the  distilling  apparatus, 
described  farther  on,  and  distilling  it  from  an  excess  of  pure  caustic  soda, 
or  determine  the  amount  of  ammonia  in  a  portion  of  hydrochloric  acid 
of  i.i  sp.  gr.,  and  use  the  amount  found  as  a  correction. 

Solution  of  Caustic  Soda,  made  by  dissolving  300  grammes  of  fused 
caustic  soda  in  500  c.c.  of  water,  and  digesting  it  for  twenty-four  hours 
at  50°  C.  on  a  copper-zinc  couple,  made,  as  described  by  Gladstone  & 
Tribe,  as  follows.  Place  from  25  to  30  grammes  of  thin  sheet  zinc  in  a 
flask  and  cover  with  a  moderately  concentrated,  slightly  warm  solution 
of  copper  sulphate.  A  thick  spongy  coating  of  copper  will  be  deposited 
on  the  zinc.  Pour  off  the  solution  in  about  ten  minutes  and  wash  thor- 
oughly with  cold  distilled  water. 

Nessler  Reagent.  Dissolve  35  grammes  of  potassium  iodide  in  a  small 
quantity  of  distilled  water,  and  add  a  strong  solution  of  mercuric  chloride 
little  by  little,  shaking  after  each  addition,  until  the  red  precipitate  formed 
dissolves.  Finally  the  precipitate  formed  will  fail  to  dissolve,  then  stop 
the  addition  of  the  mercury  salt  and  filter.  Add  to  the  filtrate  120 
grammes  of  caustic  soda  dissolved  in  a  small  amount  of  water,  and  dilute 
until  the  entire  solution  measures  I  litre.  Add  to  this  5  c.c.  of  saturated 
aqueous  solution  of  mercuric  chloride,  mix  thoroughly,  allow  the  precipi- 
tate formed  to  settle,  and  decant  or  siphon  off  the  clear  liquid  into  a 
glass- stoppered  bottle. 

Standard  Ammonia  Solution.  Dissolve  0.0382  gramme  of  ammonium 
chloride  in  I  litre  of  water.  I  c.c.  of  this  solution  will  equal  o.oi 
milligramme  of  nitrogen. 

Distilled  Water  free  from  Ammonia.     If  the   ordinary  distilled  water 


DE  TERMINA  TION  OF  NITR  O  GEN.  209 

contains  ammonia,  redistil  it,  reject  the  first  portions  coming  over,  and  use 
the  subsequent  portions,  which  will  be  found  free  from  ammonia.  Several 
glass  cylinders  of  colorless  glass  of  about  160  c.c.  capacity  are  also  required. 

The  best  form  of  distilling  apparatus  consists  of  an  Erlenmeyer  flask 
of  about  1500  c.c.  capacity,  with  a  rubber  stopper,  carrying  a  separatory 
funnel-tube  and  an  evolution-tube,  the  latter  connected  with  a  condensing- 
tube  around  which  passes  a  constant  stream  of  cold  water.  The  inside 
tube,  where  it  issues  from  the  condenser,  should  be  sufficiently  high  to  dip 
into  one  of  the  glass  cylinders  placed  on  the  working-table. 

The  determination  of  nitrogen  is  made  as  follows.  Place  30  c.c.  of  the 
caustic  soda,  which  has  been  treated  with  the  copper-zinc  couple,  in  the 
Erlenmeyer  flask,  add  500  c.c.  of  water,  and  distil  until  the  distillate  gives 
no  reaction  with  the  Nessler  reagent.  While  this  part  of  the  operation  is 
in  progress,  dissolve  3  grammes  of  the  carefully  washed  drillings  in  30  c.c. 
of  the  prepared  hydrochloric  acid,  using  heat  if  necessary.  Transfer  the 
solution  to  the  bulb  of  the  separatory  funnel-tube,  and  when  the  soda 
solution  is  free  from  ammonia,  drop  the  ferrous  chloride  solution  into  the 
boiling  solution  in  the  flask,  very  slowly.  The  ferrous  hydrate  formed  is 
apt  to  stick  to  the  bottom  and  sides  of  the  flask  and  cause  it  to  break. 
When  about  50  c.c.  of  water  have  been  collected  in  the  cylinder, 
remove  it  and  substitute  another  cylinder.  Place  I  ^  c.c.  of  the  Nessler 
reagent  in  a  cylinder,  dilute  the  distillate  to  100  c.c.  with  the  special  dis- 
tilled water  and  pour  it  into  the  cylinder  containing  the  Nessler  reagent. 
Take  another  cylinder,  place  ij£  c.c.  of  the  Nessler  reagent  in  it,  and 
pour  into  it  100  c.c.  of  the  special  distilled  water  to  which  I  c.c.  of  the 
ammonium  chloride  solution  has  been  added,  and  compare  the  colors  of 
the  solutions  in  the  two  cylinders.  If  the  solution  in  the  cylinder  con- 
taining the  ammonium  chloride  solution  is  lighter  in  color  than  that  in 
the  cylinder  containing  the  distillate,  place  \y2  c.c.  of  the  Nessler  reagent 
in  another  cylinder,  pour  into  it  100  c.c.  of  water  containing  2  or  more 
c.c.  of  the  ammonium  chloride  solution,  and  repeat  this  operation  until  the 
colors  of  the  solutions  in  the  two  cylinders  correspond  after  standing 
about  ten  minutes.  When  about  100  c.c.  have  distilled  into  the  second 

cylinder,  replace   it   and    test   as    before.     Continue   the    distillation    until 

14 


210  ANALYSIS   OF  IRON  AND   STEEL. 

the  water  comes  over  free  from  ammonia,  then  add  together  the  number 
of  c.c.  of  ammonia  solution  used,  divide  the  sum  by  3,  and  each  o.oi 
milligramme  will  be  o.ooi  per  cent,  of  nitrogen  in  the  steel. 


DETERMINATION    OF    IRON. 

The  combined  carbon  in  steel  and  iron  interferes  with  a  direct  de- 
termination of  the  amount  of  metallic  iron  by  solution  of  the  drillings 
in  hydrochloric  or  sulphuric  acid  and  direct  titration.  It  is  always  neces- 
sary to  oxidize  the  iron  and  carbonaceous  matter  in  the  solution,  and  the 
process  may  be  carried  out  as  follows : 

Dissolve  .5  gramme  of  the  drillings  in  a  small  flask,  as  described  for 
the  determination  of  iron  in  iron  ores,  in  hydrochloric  acid,  add  potas- 
sium chlorate  in  small  crystals  until  the  iron  is  all  oxidized  and  an 
excess  of  potassium  chlorate  is  present,  boil  until  all  the  yellow  fumes 
have  disappeared,  and  then  proceed  as  in  the  determination  of  iron  in 
iron  ores  (page  224).  Instead  of  potassium  chlorate,  potassium  perman- 
ganate or  chromic  acid  may  be  used  to  oxidize  the  iron  and  destroy  the 
carbonaceous  matter.  In  pig-irons  the  most  satisfactory  method  is  to 
fuse  .5  gramme  of  the  borings  in  a  large  platinum  crucible  with  10 
grammes  sodium  carbonate  and  2  grammes  potassium  nitrate,  dissolve  in 
hot  water,  transfer  to  a  small  beaker,  allow  the  ferric  oxide  to  settle, 
decant  on  a  small  filter,  and  wash  several  times  by  decantation.  After 
the  last  decantation,  remove  the  beaker  containing  the  filtrate  and  place 
the  beaker  containing  the  ferric  oxide  under  the  funnel.  Dissolve  any 
adhering  oxide  in  the  crucible  with  hydrochloric  acid,  dilute  slightly, 
and  pour  it  on  the  filter  to  dissolve  the  small  amount  of  oxide,  allow- 
ing the  solution  to  run  into  the  beaker.  Wash  the  filter  if  necessary, 
add  more  hydrochloric  acid  to  the  solution  in  the  beaker,  evaporate 
down,  transfer  to  a  small  flask,  deoxidize,  and  titrate  as  before.  In  the 
case  of  puddled  iron,  it  is  necessary  to  subtract  the  iron  in  the  "  slag 
and  oxides"  from  the  total  iron  obtained  as  above  to  get  the  amount  of 
metallic  iron  in  the  sample. 


METHODS  FOR  THE  ANALYSIS 


OF 


CHROME-TUNGSTEN  STEELS. 


BESIDES  chromium  and  tungsten,  these  steels  may  contain  nickel, 
vanadium,  and  molybdenum,  as  well  as  the  ordinary  elements,  manganese, 
silicon,  sulphur,  phosphorus,  and  carbon. 


DETERMINATION   OF  CARBON. 

The  best  method  for  the  determination  of  carbon  is  the  direct  combus- 
tion in  oxygen  as  given  on  page  1 34  et  seq.  The  double  chloride  method 
gives  results  from  10  per  cent,  to  40  per  cent,  too  low. 


DETERMINATION   OF  SULPHUR. 

The  evolution   method  is  practicable  and   accurate  for  steels  of  this 


character. 


DETERMINATION  OF  SILICON  AND  TUNGSTEN. 

Treat  2  grammes  of  the  drillings  with  50  c.c.  of  hydrochloric  and  15  c.c. 
of  nitric  acid  in  a  400  c.c.  beaker.  Heat  gently  until  the  material  is  de- 
composed and  the  tungstic  acid,  if  it  separates,  is  bright  yellow  in  color. 
Evaporate  to  dryness  but  do  not  bake.  Redissolve  in  20  c.c.  of  hydro- 
chloric acid,  add  a  few  drops  of  nitric  acid,  and  boil  for  a  few  minutes. 
Add  100  c.c.  of  hot  water  and  boil.  Filter,  wash  thoroughly  with  water 
containing  150  c.c.  of  hydrochloric  acid  to  the  litre.  Dissolve  any  tungstic 
acid  that  adheres  too  firmly  to  the  beaker  to  be  rubbed  off,  in  ammonia,  wash 
it  into  a  weighed  crucible,  and  evaporate  to  dryness.  Place  the  precipitate 

211 


2 1 2  ANAL  YSIS  OF  IRON  AND  STEEL. 

of  tungstic  acid  which  has  been  filtered  and  washed  in  the  crucible  and 
ignite  it.  In  the  mean  time  evaporate  the  filtrate  to  dryness  and  heat  to 
render  the  silica  insoluble.  Redissolve  in  15  c.c.  hydrochloric  acid  and  if 
the  solution  is  to  be  used  for  the  determination  of  phosphorus  or  manga- 
nese, drive  off  the  hydrochloric  acid  by  repeated  evaporations  with  nitric 
acid.  Evaporate  to  syrupy  consistency  and  dissolve  in  50  c.c.  of  nitric 
acid  (1.135  sp.  gr.).  Filter  into  a  flask,  wash  with  50  c.c.  of  the  same  acid, 
add  the  precipitate  to  the  ignited  precipitate  in  the  crucible,  burn  and 
weigh.  If  the  solution  is  to  be  used  for  the  determination  of  the  chro- 
mium, nickel,  etc.,  instead  of  evaporating  off  the  hydrochloric  acid  with 
nitric  acid,  add  a  few  drops  of  nitric  acid  and  100  c.c.  of  water,  boil  for 
ten  minutes,  filter  and  wash  as  before.  Add  this  precipitate  to  the  other, 
ignite  and  weigh.  Treat  the  precipitate  with  hydrofluoric  and  a  few  drops 
of  sulphuric  acid,  evaporate  carefully  to  dryness,  ignite  and  weigh.  The 
loss  of  weight  is  silica,  which  multiplied  by  .4702  gives  the  weight  of  the 
silicon.  Fuse  the  mass  in  the  crucible  with  sodium  carbonate  and  a  little 
potassium  nitrate.  Dissolve  in  water,  filter,  wash  well  with  hot  water, 
return  the  insoluble  to  the  crucible,  ignite  and  weigh.  The  difference 
between  this  and  the  last  weight  is  tungstic  acid,  which  multiplied  by 
•793 l  gives  the  weight  of  tungsten. 


DETERMINATION   OF  PHOSPHORUS. 

Treat   the   nitric  acid   solution   in  the  flask   exactly  as   described  on 
page  92  et  seq. 


DETERMINATION   OF  MANGANESE. 

Treat  the  nitric  acid  solution  by  Ford's  method,  page  113  ct  seq. 


DETERMINATION  OF  CHROMIUM. 

Evaporate  the  hydrochloric  acid  filtrate,  as  noted  above,  to  syrupy  con- 
sistency, and  separate  the  chromium  oxide  by  the  ether  method,  page  194. 


ANALYSIS  OF  CHROME  TUNGSTEN  STEELS.  21 3 

DETERMINATION    OF    NICKEL,  CHROMIUM, 
AND  MANGANESE. 

When  nickel,  chromium,  and  manganese  are  present  and  all  are  to  be 
determined,  the  best  method  of  procedure  is  to  evaporate  nearly  to  dry- 
ness  the  hydrochloric  acid  solution  after  the  separation  by  ether.  Trans- 
fer it  to  a  platinum  crucible,  evaporate  to  dryness,  heat  to  dull  redness,  and 
fuse  the  mass  in  the  crucible  with  sodium  carbonate  and  potassium 
nitrate.  Treat  the  fused  mass  with  water  and  filter.  The  iron,  the  nickel, 
and  part  of  the  manganese  remain  insoluble,  while  the  chromium  and  the 
rest  of  the  manganese  are  in  the  filtrate.  Evaporate  this  filtrate  with 
ammonium  nitrate  as  described  on  page  194,  and  filter.  Dissolve  the 
insoluble  matter  on  the  filter  in  hydrochloric  acid  and  add  to  it  the  hydro- 
chloric acid  solution  of  the  insoluble  matter  left  by  the  fusion  as  described 
above.  Determine  the  chromium  in  the  filtrate  from  the  ammonium  nitrate 
as  directed  on  page  194.  Evaporate  to  dryness  the  hydrochloric  acid 
solution  of  the  nickel,  manganese,  and  iron,  redissolve  in  a  little  hydro- 
chloric acid,  dilute,  and  separate  the  iron  from  the  nickel  and  manganese 
by  sodium  acetate.  In  the  filtrate  from  the  iron  precipitate  the  nickel  by 
hydrogen  sulphide.  Filter,  wash,  ignite  the  nickel  sulphide,  redissolve  in 
hydrochloric  acid,  and  evaporate  until  it  fumes  freely.  Determine  the 
nickel  by  electrolysis.  Boil  the  filtrate  from  the  nickel  sulphide  to  expel  the 
hydrogen  sulphide  and  precipitate  the  manganese  by  bromine.  Filter  and 
determine  the  manganese  as  described  on  page  no,  or  dissolve  the  washed 
precipitate  of  manganese  dioxide  in  sulphurous  acid,  evaporate  with  nitric 
acid,  and  determine  the  manganese  by  the  bismuthate  method,  page  122. 


DETERMINATION  OF  VANADIUM. 

Treat  2  grammes  of  drillings  as  for  chromium  and  evaporate  to  dryness 
the  hydrochloric  acid  solution  from  the  ether  separation  after  adding  a 
little  nitric  acid.  Repeat  the  evaporation  with  hydrochloric  acid  twice  and 
determine  the  vanadium  as  directed  on  page  202. 


214  ANAL  YSIS  OF  IRON  AND  STEEL. 

SEPARATION   OF  CHROMIUM   AND  VANADIUM. 

Campagne*  gives  a  method  for  the  separation  of  chromium  and  vana- 
dium which  is  quite  accurate  when  the  chromium  is  not  present  in  too  great 
an  amount.  The  method  is  based  on  the  fact  that  the  di-vanadyl  sulphate 
is  oxidized  readily  in  the  cold  by  potassium  permanganate,  while  the 
chromium  is  not  affected.  Titrate  the  solution  obtained  above  for  vana- 
dium in  the  cold,  then  add  a  large  excess  of  potassium  permanganate 
and  boil  vigorously  to  oxidize  the  chromium  sulphate  to  chromic  acid 
and  the  di-vanadyl  sulphate  to  vanadic  sulphate.  The  solution  should 
remain  pink  in  color  after  boiling.  Then  add  a  small  amount  of  paper 
pulp  to  reduce  the  permanganate  and  filter.  To  the  cold  filtrate  add 
an  excess  of  standardized  ammonium  ferrous  sulphate  and  titrate  the 
excess  of  ferrous  salt  with  permanganate.  The  difference  is  the  amount 
of  the  ferrous  salt  oxidized  by  the  chromic  acid. 

2CrO3  +  6FeS04  -f-  6H2SO4  ===  O2(SO4)3  -f  3Fe2(SO4)3  +  6H2O  and 
ioFeSO4  +  2KMnO4  +  8H2SO4  ==  5Fe2(SO4)3  -f-  K2SO4  -f  2MnSO4-{- 
8H2O,  whence  3  equivalents  of  iron  1 68  =  I  equivalent  of  chromium  52.14, 
or  the  value  in  iron  of  the  permanganate  equivalent  to  the  ferrous  sulphate 
oxidized  by  the  chromic  acid  multiplied  by  .3103  equals  the  chromium. 

The  vanadium  has  no  influence  on  this  result,  because  the  vanadic  sul- 
phate which  is  reduced  to  vanadyl-sulphate  by  the  ferrous  sulphate  is  re- 
oxidized  by  the  permanganate  in  the  cold  solution,  while  the  chromium 
sulphate  is  not  affected. 


*  Bull.  Soc.  Chem.,  series  iii.,  vol.  xxxi.,  No.  16. 


METHODS  FOR  THE  ANALYSIS 


OF 


FERRO-TUNGSTEN  AND  TUNGSTEN  METAL 


DETERMINATION   OF  CARBON 

Mix  one  gramme  of  the  finely  ground  metal  with  2  grammes  of  finely 
divided  low-carbon  steel,  or,  better,  with  finely  powdered  electrolytic  iron,  and 
burn  it  in  the  manner  described  for  the  determination  of  carbon  in  steel  by 
direct  combustion  in  a  current  of  oxygen,  page  134.  The  electrolytic  iron 
made  by  Prof.  Burgess  is  admirable  for  this  purpose,  for  it  contains  only 
about  0.030  per  cent,  carbon  and  can  be  reduced  to  a  very  fine  powder. 
Of  .course,  the  amount  of  carbon  in  the  steel  or  iron  used  must  be  sub- 
tracted from  the  amount  obtained  by  combustion  of  the  mixture. 


DETERMINATION  OF  TUNGSTEN. 

Ferro-tungsten  may  be  treated*  exactly  like  chrome-tungsten  steels,  but 
tungsten  metal  may  be  fused  (.5  gramme)  with  sodium  carbonate  and  potas- 
sium nitrate  and  the  tungsten  determined  by  precipitation  with  mercurous 
nitrate,  as  on  page  201. 

Tungsten  metal  is  insoluble  in  nitric  acid  alone,  but  the  addition  of  a  few 
drops  of  hydrofluoric  acid  causes  it  to  dissolve  completely.  An  alternate 
method  is  based  on  this  fact.  Place  .5  gramme  of  the  finely  ground  metal 
in  a  large  platinum  crucible,  add  25  c.c.  nitric  acid  (1.2  sp.  gr.),  and  heat 
carefully.  Add  a  few  drops  of  hydrofluoric  acid  and,  when  decomposition 
is  complete,  add  a  few  drops  of  sulphuric  acid,  evaporate  to  dryness,  heat 

215 


2l6  ANALYSIS  OF  IRON  AND  STEEL. 

to  redness  and  weigh.  Fuse  with  sodium  carbonate  and  a  little  potassium 
nitrate,  cool,  dissolve  in  water,  filter,  wash,  return  the  filter  and  contents  to 
the  crucible,  ignite  and  weigh.  The  difference  between  the  weights  is 
tungstic  acid. 


DETERMINATION  OF  THE  OTHER  ELEMENTS. 

As  ferro-tungsten  and  tungsten  metal  are  decomposed  by  aqua  regia,  the 
other  elements  may  be  determined  as  in  chrome-tungsten  steel,  with  the 
exception  of  sulphur. 


DETERMINATION    OF  SULPHUR. 

As  tungsten  metal  is  insoluble  in  hydrochloric  acid,  the  sulphur  must 
be  determined  by  treating  I  to  2  grammes  with  aqua  regia,  as  for  the  deter- 
mination of  silicon  in  chrome-tungsten  steels,  page  211.  Evaporate  the 
solution  from  the  silicon  determination  almost  to  dryness,  take  up  in  4  c.c. 
of  hydrochloric  acid,  dilute  to  100  c.c.  with  hot  water,  heat  to  boiling,  and 
precipitate  by  barium  chloride  solution.  Determine  the  sulphur  as  on 
page  66. 


METHODS   FOR  THE  ANALYSIS 

OF 

FERRO-CHROME,    FERRO-SILICON,   AND 
FERRO-TITANIUM. 


DETERMINATION    OF    CARBON. 

CARBON  may  be  determined  with  a  considerable  degree  of  accuracy  in 
some  of  these  alloys  by  combustion  with  lead  chromate  and  potassium 
chlorate  in  a  glass  tube,  as  described  on  page  129.  The  best  method,, 
however,  is  by  direct  combustion  as  described  for  tungsten  metal  (page  216). 


DETERMINATION    OF   SULPHUR. 

Fuse  2  grammes  of  the  sample  ground  as  fine  as  possible  in  an 
agate  mortar  with  15  grammes  of  sodium  peroxide  in  a  large  nickel 
crucible.  The  heat  should  be  applied  very  slowly  and  cautiously,  as 
sodium  peroxide  gives  up  its  oxygen  at  a  low  temperature  and  the 
amount  of  heat  generated  by  the  oxidation  of  the  chromium,  silicon,  etc., 
of  the  alloys  is  very  great.  An  alcohol  blast-lamp  should  be  used,  as 
the  sulphur  in  ordinary  gas  is  liable  to  vitiate  the  result.  As  soon  as 
the  mass  is  liquid,  raise  the  heat  for  a  few  minutes,  run  the  fused  mass 
well  up  on  the  sides  of  the  crucible,  and  allow  it  to  cool.  Stand  the 
crucible  in  a  400  c.c.  beaker  containing  a  little  water,  partly  cover  the 
beaker  with  a  watch-glass,  and  throw  a  fine  stream  of  cold  water  into  the 
crucible  from  a  wash-bottle.  When  the  violent  action  has  ceased,  wash 

217 


2l8  ANALYSIS    OF  IRON  AND   STEEL. 

the  fusion  from  the  crucible  and  filter  from  the  insoluble  ferric  oxide, 
etc.,  washing  the  insoluble  matter  with  water  containing  a  little  sodium 
carbonate.  Acidulate  the  filtrate  with  hydrochloric  acid  and  evaporate  to 
dryness,  preferably  in  a  porcelain  beaker.  When  thoroughly  dry,  cool, 
add  20  c.c.  of  strong  hydrochloric  acid,  and  heat  until  in  the  case  of 
ferro-chrome  all  the  chromium  is  redissolved.  Dilute  with  hot  water, 
filter,  wash  thoroughly  with  hot  water,  neutralize  with  ammonia,  add  20  or 
30  drops  of  hydrochloric  acid,  heat  to  boiling,  add  10  c.c.  of  a  boiling 
saturated  solution  of  barium  chloride,  and  boil  for  half  an  hour.  Allow 
the  solution  to  stand  in  a  warm  place  overnight,  filter,  wash  thoroughly, 
ignite,  and  weigh  the  barium  sulphate. 


DETERMINATION    OF    SILICON. 

Ferro-silicon  which  is  capable  of  being  decomposed  by  acids  is 
treated  like  steel,  except  that  from  i  to  2  grammes  is  sufficient  for 
the  determination  of  silicon.  For  those  not  decomposed  by  acids 
and  for  ferro-chrome  and  ferro-titanium  proceed  as  follows.  Fuse 
I  gramme  with  10  grammes  of  sodium  peroxide,  treat  with  water, 
and  finally  with  hydrochloric  acid.  Evaporate  to  dryness  in  a  plati- 
num or  porcelain  dish.  When  platinum  is  used  for  the  evaporation, 
it  is  best  to  add  an  excess  of  sulphurous  acid  to  the  solution  to 
prevent  action  on  the  platinum  by  the  chlorine  liberated  by  the  action 
of  the  hydrochloric  acid  on  the  chromic  or  manganic  acid  in  the 
solution. 

Redissolve  in  hydrochloric  acid  and  water,  filter,  wash,  ignite,  and 
weigh.  Treat  the  weighed  silica,  etc.,  in  the  crucible  with  hydrofluoric 
and  sulphuric  acids,  evaporate  to  dryness,  ignite,  and  weigh.  The 
difference  between  the  two  weights  is  silica,  which  contains  47.02  per 
cent,  of  silicon. 

In  ferro-titanium,  when  filtering  off"  the  silica,  etc.,  the  greater  part 
of  the  titanic  acid  will  be  with  the  silica,  and  as  it  has  a  tendency 
to  pass  through  the  filter  when  washed  with  water,  the  washing  must 
be  done  with  dilute  hydrochloric  acid.  Instead  of  treating  the  ignited 


DETERMINATION  OF  PHOSPHORUS.  219 

residue  with  hydrofluoric  and  sulphuric  acids,  it  is  better  to  fuse  it 
with  potassium  bisulphate,  which  dissolves  the  titanic  acid;  dissolve 
the  fused  mass  in  water,  filter,  ignite,  and  weigh  the  silica  as  above. 


DETERMINATION    OF    PHOSPHORUS. 

In  Ferro-Chrome. 

Fuse  2  grammes  of  the  finely  ground  material  with  15  grammes 
of  sodium  peroxide  in  a  nickel  crucible,  and  treat  it  with  water  as 
directed  for  the  determination  of  sulphur.  The  aqueous  solution  will 
contain  sodium  chromate  and  phosphate,  besides  silica,  etc.  Filter, 
and  wash  with  water  containing  a  little  sodium  carbonate.  Acidulate 
the  filtrate  with  nitric  acid,  heat  to  drive  off  the  carbonic  acid,  add 
a  little  ferric  chloride  solution,  add  ammonia  until  the  solution  is 
alkaline  to  litmus-paper,  and  then  acidulate  with  acetic  acid.  Boil  for 
a  few  minutes,  filter,  and  wash  the  precipitate  of  ferric  phosphate  and 
hydrate  with  hot  water.  Dissolve  the  precipitate  on  the  filter  in  hot 
dilute  hydrochloric  acid,  evaporate  the  solution  to  dryness,  redissolve 
in  a  few  drops  of  hydrochloric  acid,  and,  if  there  is  an  appreciable 
amount  of  silica,  dilute  and  filter,  evaporate  to  a  small  bulk,  and  drive 
off  the  hydrochloric  acid  with  nitric  acid.  In  the  absence  of  any 
material  amount  of  silica,  omit  the  filtration,  add  nitric  acid,  and 
evaporate  to  get  rid  of  the  hydrochloric  acid.  Transfer  the  nitric 
acid  solution  to  a  flask,  precipitate  by  molybdate  solution,  and  determine 
the  phosphorus  as  described  on  page  92  ct  seq. 

In  Ferro-Silicon. 

Fuse  2  grammes  with  sodium  peroxide  as  described  above,  treat 
with  water,  and  filter.  As  the  solution  contains  a  large  amount  of 
silica,  evaporate  to  dryness  after  acidulating  with  hydrochloric  acid, 
redissolve  in  water  and  hydrochloric  acid,  and  filter.  To  the  filtrate 
add  a  little  ferric  chloride  solution,  and  proceed  as  in  the  case  of 
ferro-chrome. 


220  ANAL  YSIS    OF  IRON  AND   STEEL. 

In  Ferro-Titanium. 

Fuse  2  grammes  as  described  above,  treat  with  water,  and  filter. 
The  titanic  acid  will  be  insoluble  as  sodium  titanate.  Acidulate  the 
filtrate  with  hydrochloric  acid,  add  ferric  chloride  solution,  and  pro- 
ceed as  in  the  case  of  ferro-silicon. 


DETERMINATION    OF    MANGANESE. 

Proceed  as  in  the  determination  of  silicon,  and,  after  filtering  off 
the  silica,  evaporate  the  filtrate  nearly  to  dry  ness,  add  nitric  acid  and 
evaporate  ofT  the  hydrochloric  acid,  precipitate  by  potassium  chlorate> 
and  determine  the  manganese  as  in  Ford's  method  (page  113). 


DETERMINATION    OF   CHROMIUM. 

Gravimetric  Method. 

Fuse  .5  gramme  with  5  grammes  of  sodium  peroxide  in  a  nickel 
crucible,  treat  with  water,  and  filter.  If  the  residue  insoluble  in  water 
does  not  dissolve  completely  in  hydrochloric  acid,  filter,  ignite,  and 
fuse  the  residue  in  sodium  peroxide.  Dissolve  in  water,  and  if  the 
solution  is  yellow,  filter  and  add  the  filtrate  to  the  first  filtrate. 

To  the  united  filtrates  add  ammonium  nitrate  in  sufficient  quantity 
to  convert  all  the  sodium  salts  into  nitrates,  boil  until  the  excess  of 
ammonia  is  driven  off,  filter,  and  to  the  filtrate  in  a  large  platinum  or 
porcelain  dish  add  an  excess  of  sulphurous  acid.  This  will  reduce  all 
the  chromic  acid  to  chromium  sesquioxide.  Boil  off"  the  sulphurous 
acid,  add  an  excess  of  ammonia,  boil,  filter,  and  wash  thoroughly  with 
boiling  water.  Dissolve  the  precipitate  in  hot  hydrochloric  acid,  evapo- 
rate to  dryness,  redissolve  in  hydrochloric  acid,  filter,  and  reprecipitate 
with  ammonia.  Boil,  filter,  wash,  and  ignite.  Transfer  the  precipi- 
tate to  a  small  beaker  with  water,  add  a  little  ammonium  nitrate  and 
a  few  drops  of  sulphurous  acid,  and  boil  until  the  solution  no  longer 


D E  TERMINA  TION  OF  IR  ON.  2  2 1 

smells  of  sulphurous  acid.  Add  a  little  ammonia,  boil,  filter,  wash 
with  water  containing  ammonium  nitrate,  ignite,  and  weigh  as  chromium 
sesquioxide,  which  contains  68.48  per  cent,  of  chromium. 

Volumetric  Method. 

Fuse  .5  gramme  as  above,  treat  with  water,  filter,  and  wash. 
Boil  the  filtrate  thoroughly  to  decompose  all  the  sodium  peroxide, 
acidulate  with  sulphuric  acid,  cool,  add  an  excess  of  ferrous  sulphate, 
and  titrate  with  a  standard  solution  of  potassium  bichromate.  The 
chromium  is  calculated  as  in  the  volumetric  method  for  chromium 
in  steel  (page  194  et  seg.). 

The  use  of  permanganate  is  inadmissible,  as  the  intense  green 
color  of  the  solution  masks  the  end  reaction. 


DETERMINATION   OF  IRON. 

Fuse  .5  gramme  of  the  fine  powder  in  a  platinum  crucible  with 
5  grammes  of  sodium  peroxide.  Do  not  heat  the  fusion  after  it  has 
become  liquid,  as  the  sodium  peroxide  cuts  the  platinum  crucible.  A 
nickel  crucible  cannot  be  used,  as  all  nickel  crucibles  contain  appreciable 
amounts  of  iron,  so  that  the  amount  of  iron  derived  from  the  nickel 
depends  on  the  extent  of  the  action  on  the  crucible.  Treat  the  fused  mass 
with  water  and  filter.  Dissolve  the  residue,  which  contains  all  the  iron, 
in  hydrochloric  acid,  reduce  with  zinc,  and  titrate  with  permanganate  in 
the  usual  way. 

In  ferro-titanium,  as  the  titanic  acid  is  with  the  iron,  it  cannot  be 
reduced  with  zinc,  and  reduction  with  ammonium  sulphite,  as  in  the  case 
of  titaniferous  iron  ores  (page  227),  must  be  resorted  to. 


METHODS   FOR  THE  ANALYSIS 

OF 

IRON    ORES. 


A  FEW  words  in  regard  to  the  proper  method  of  taking  samples  of 
iron  ores  may  not  be  amiss,  for  unless  the  sample  truly  represents  the  lot 
from  which  it  is  taken,  the  subsequent  work  of  the  analyst  is  useless,  if 
not  misleading. 

In  drawing  a  sample,  note  carefully  the  relative  amounts  of  fine  ore 
and  lumps  in  the  lot  to  be  sampled,  and  see  that  this  proportion  be 
observed  in  the  whole  amount  taken.  A  small  trowel  may  be  used  for 
taking  the  fine  ore,  and  only  about  a  teaspoonful  should  be  picked  up  at 
one  time.  In  taking  pieces  from  the  lumps,  it  will  never  do  to  merely 
chip  the  outside,  but  each  lump  as  selected  should  be  broken  and  chippings 
no  larger  than  a  cherry  taken  from  both  the  inside  and  the  outside.  In 
sampling  from  cars  or  wagons  these  points  should  be  observed  in  each  car 
or  wagon,  for  it  is  rarely  the  case  that  the  ore  even  from  one  mine  is  so 
uniform  as  to  render  this  precaution  unnecessary.  In  some  cases  the 
lumps  are  covered  with  dirt  or  gangue,  making  the  outside  of  the  lump 
poorer  in  iron  than  the  inside,  and  on  the  other  hand  the  lumps  are  merely 
masses  of  dirt  coated  with  ore.  Then  the  fine  stuff  may  be  much  richer 
than  the  lumps,  or  it  may  be  merely  dirt  or  gangue,  while  it  almost  always 
contains  more  hygroscopic  water  than  the  lumps.  The  sample  should  be 
taken  in  tin  cans  with  close-fitting  lids,  and  the  amount  should  be  propor- 
tioned to  the  size  of  the  lot  sampled.  Two  pounds  to  ten  tons  is  a  good 
rule  for  large  lots. 

222 


DETERMINATION   OF  HYGROSCOPIC  WATER. 


223 


DETERMINATION    OF    HYGROSCOPIC    WATER. 

Break  the  sample  down  quickly  to  about  pea  size,  mix  thoroughly  in 
a  large  glazed  earthenware  or  metal  dish,  and  weigh  out  from  ^  to  I  kilo, 
into  a  copper  box  about  4^  inches  (114  mm.)  long,  3^  inches  (95  mm.) 
wide,  and  \y2  inches  (38  mm.)  deep,  and  dry  in  a  water-  or  air-bath  at 
100°  C.  for  at  least  twelve  hours,  or  until  it  ceases  to  lose  weight.  Fig. 
95  shows  a  convenient  form  of  water-bath.  The  boxes  are  numbered,  and 

FIG.  95. 


each  one  is  provided  with  a  counterpoise  stamped  with  the  same  number 
as  the  box,  to  facilitate  the  weighing.  When  a  supply  of  water  is  not 
available  to  run  the  constant  level  shown  in  Fig.  95,  the  device,  on  the 
principle  of  Mariotte's  flask,  as  shown  in  Fig.  86,  page  177,  may  be  used. 
The  position  of  the  end  b  of  the  tube  a  fixes  the  level  of  the  water  in  the 
bath. 


224  ANALYSIS   OF  IRON  ORES. 

A  balance  sensitive  to  .1  gramme  is  sufficiently  accurate  for  weighing 
these  samples.  The  loss  of  weight  in  grammes  divided  by  5,  when  y2 
kilo,  of  ore  was  originally  used,  gives  the  percentage  of  hygroscopic  water 
in  the  sample.  Grind  the  dried  sample  very  fine,  mix  it  well,  heat  as  much 
of  it  as  may  be  required  for  the  analysis  in  the  water-bath,  and  put  it 
while  still  hot  into  a  perfectly  dry,  glass-stoppered  bottle. 


DETERMINATION    OF   TOTAL   IRON. 

Very  few  iron  ores  are  completely  decomposed  by  hydrochloric  acid, 
the  insoluble  residue  usually  containing  more  or  less  iron,  as  silicate, 
titaniferous  iron,  etc.  The  disregard  of  this  fact  may  occasion  grave 
errors  in  the  determination  of  iron,  and,  unless  a  previous  examination 
has  shown  the  absence  of  iron  in  the  insoluble  residue,  it  is  best  to  pro- 
ceed as  follows.  Place  I  gramme  of  the  finely  ground  sample  in  a  No. 
I  beaker,  add  10  c.c.  hydrochloric  acid,  and  digest  it  on  the  hot  plate 
until  the  residue  appears  quite  white  and  flotant,  or  until  the  acid  ap- 
pears to  have  no  further  action.  When  the  ore  contains  carbonaceous 
matter,  add  a  little  potassium  chlorate.  Wash  off  the  watch-glass  with 
a  fine  jet  of  water,  remove  it,  and  evaporate  to  dryness  in  the  air-bath. 
Redissolve  in  about  5  c.c.  hydrochloric  acid,  dilute  with  10  c.c.  water, 
allow  to  settle,  and  decant  the  clear  liquid  into  a  flask  of  from  50  to 
75  c.c.  capacity.  Transfer  the  residue  to  a  small  filter,  fitted  in  a  funnel 
placed  in  the  neck  of  the  flask,  with  as  little  water  as  possible,  and  wash 
with  cold  water  from  a  fine  jet.  Transfer  the  filter  to  a  small  platinum 
crucible,  burn  it  off,  allow  the  crucible  to  cool,  and  pour  on  the  residue 
20  or  30  drops  of  sulphuric  acid  and  about  twice  as  much  hydrofluoric 
acid.  Heat  carefully,  and,  if  the  residue  is  dissolved,  evaporate  off  the 
hydrofluoric  acid,  allow  the  liquid  to  cool,  and  dilute  slightly,  when  it  will 
be  ready  to  add  to  the  solution  in  the  flask,  which  will  have  been  deoxi- 
dized in  the  mean  time  by  one  of  the  methods  explained  farther  on. 

Occasionally  this  treatment  fails  to  decompose  the  insoluble  residue, 
in  which  case  heat  the  crucible  until  the  greater  part  of  the  sulphuric 


DETERMINATION  OF   TOTAL    IRON.  22$ 

acid  is  driven  off;  then  add  about  .5  gramme  potassium  bisulphate,  and 
heat  gradually  until  the  potassium  bisulphate  is  quite  liquid  and  fumes 
of  sulphuric  acid  are  given  off  whenever  the  lid  of  the  crucible  is  raised. 
When  all  the  black  specks  have  disappeared,  allow  the  crucible  to  cool, 
and  dissolve  the  salt  in  the  crucible  with  hot  water  and  a  few  drops  of 
hydrochloric  acid. 

Several  methods  are  used  for  the  deoxidation  of  the  solution  of  ferric 
chloride,  but  the  one  in  general  use  is  by  adding  metallic  zinc  to  the 
solution.  The  iron  is  deoxidized  according  to  the  reaction  Fe2Cl6  +  Zn 
=  2FeCl2  -f-  ZnCl2,  while  the  excess  of  hydrochloric  acid  is  decomposed 
and  hydrogen  liberated,  2HC1  +  Zn  =  ZnCl2  -f  2H.  As  all  zinc  contains 
a  small  amount  of  iron,  the  amount  added  to  the  solution  should  be 
roughly  weighed.  Add  then  to  the  solution  in  the  flask  3  grammes  of 
granulated  zinc,*  and,  when  the  evolution  of  hydrogen  has  somewhat 
slackened,  heat  the  flask  slightly.  The  neck  of  the  flask  is  closed  by  a 
small  funnel,  which  allows  the  hydrogen  to  escape  while  the  liquid  is 
caught  on  the  funnel  and  falls  back  into  the  flask.  It  sometimes  hap- 
pens as  the  solution  becomes  neutralized  that  a  basic  salt  of  ferric  oxide 
is  thrown  down,  giving  the  solution  a  reddish  color;  in  this  case  add  a 
few  drops  of  hydrochloric  acid,  and  when  the  solution  finally  becomes 
colorless  add  a  few  drops  more  of  hydrochloric  acid.  If  this  fails  to 
produce  a  yellowish  coloration,  the  solution  may  be  considered  deoxi- 
dized. Pour  in  through  the  funnel  the  solution  of  the  residue  insoluble 
in  hydrochloric  acid,  and  add  gradually  a  mixture  of  10  c.c.  sulphuric 
acid  and  20  c.c.  water.  This  addition  of  sulphuric  acid  is  a  very  neces- 
sary part  of  the  operation,  for  it  not  only  serves  to  dissolve  the  remainder 
of  the  zinc  which  is  unacted  on  when  the  deoxidation  is  complete,  but  it 
supplies  the  proper  amount  of  zinc  sulphate,  which  makes  the  end  reac- 
tion with  potassium  permanganate  as  sharp  as  if  no  hydrochloric  acid 
were  present  in  the  solution.  As  soon  as  all  the  zinc  is  dissolved,  wash 
down  the  funnel  inside  and  out  and  the  neck  of  the  flask  with  a  fine  jet 
of  water,  filling  the  flask  almost  full,  cool  the  flask  in  water,  and  when 


*  See  page  58. 


226  ANAL  YSIS    OF  IRON  ORES. 

the  solution  is  quite  cold  transfer  it  to  a  large  white  dish  of  about  1500 
c.c.  capacity.  Wash  the  flask  and  funnel  well  with  cold  water,  pour  the 
rinsing  into  the  dish,  and  make  the  solution  up  to  about  1000  c.c.  Run 
in  from  a  burette  a  standard  solution  of  potassium  permanganate  (Mar- 
guerite's method),  the  value  of  which  has  been  carefully  determined  by 
one  of  the  methods  described  farther  on.  At  first  the  color  of  the  per- 
manganate is  destroyed  almost  as  soon  as  it  touches  the  liquid  in  the 
dish,  which  should  be  stirred  carefully  with  a  glass  rod.  The  perman- 
ganate should  be  added  more  and  more  slowly  until  towards  the  end  of 
the  operation  it  is  added  only  drop  by  drop.  The  liquid  in  the  dish  gradu- 
ally assumes  a  yellowish  tint,  which  is  deeper  the  larger  the  amount  of  iron 
in  the  ore.  Finally  a  drop  of  the  permanganate  seems  to  destroy  the 
yellow  color,  and  the  next  drop  gives  the  liquid  a  very  faint  pink  tinge. 
This  is  the  end  of  the  reaction.  Take  the  reading  of  the  burette,  and  then 
add  another  drop,  which  will  cause  the  solution  to  become  decidedly  pink 
in  color.  The  number  of  c.c.  of  the  standard  solution  used  when  the  read- 
ing was  taken,  less  a  small  correction  for  the  zinc,  etc.,  noted  farther  on, 
multiplied  by  the  value  of  I  c.c.,  gives  the  amount  of  metallic  iron  in 
the  ore. 

The  simple  form  of  reductor  (Fig.  52)  shown  on  page  94  may  be  used 
for  deoxidizing  the  solution  of  the  ore  in  which  the  iron  is  in  the  form  of 
sulphate.  With  amalgamated  zinc  it  is  a  most  excellent  and  rapid  device. 
The  method  of  reduction  is  given  on  page  95  in  the  description  of  the 
method  of  standardizing  the  potassium  permanganate  solution. 

When  using  a  standard  solution  of  potassium  bichromate  (Penny's 
method),  the  end  reaction  is  not  rendered  apparent  by  a  change  in  the 
color  of  the  solution,  but  the  presence  or  absence  of  ferrous  salt  in  the 
solution  is  determined  by  taking  a  drop  from  the  dish  on  the  end  of 
the  stirring-rod  and  allowing  it  to  run  into  a  drop  of  a  dilute,  freshly 
made  solution  of  potassium  ferricyanide  placed  on  a  white  tile  or  cap- 
sule. Dissolve  a  very  small  crystal  of  potassium  ferricyanide  in  a  few 
c.c.  of  water,  and  place  a  number  of  drops  of  the  solution  on  a  white 
tile  or  on  a  flat-bottomed  capsule.  Run  the  carefully  standardized  solution 
of  potassium  bichromate  from  the  burette  into  the  deoxidized  iron  solution 


DETERMINATION  OF   TOTAL    IRON.  22/ 

previously  placed  in  a  white  dish.  The  solution,  at  first  colorless,  changes 
gradually  to  a  decided  chrome-green  from  the  reduction  of  the  chromic 
acid.  Test  the  progress  of  the  oxidation  of  the  iron  solution  by  transfer- 
ring a  drop  of  it  on  the  end  of  the  stirring-rod  to  one  of  the  drops  of  fern- 
cyanide.  As  the  blue  color  produced  becomes  less  intense,  add  the  bichro- 
mate more  slowly  and  make  the  test  more  frequently,  towards  the  end  of 
the  operation  after  the  addition  of  each  drop  of  bichromate.  When,  finally, 
no  color  appears  in  the  test-drops,  even  after  the  lapse  of  several  moments, 
the  oxidation  of  the  ferrous  salt  is  complete,  and  the  amount  of  bichromate 
used,  less  a  small  correction  for  the  zinc,  is  the  measure  of  the  amount  of 
iron  in  the  ore.  The  potassium  ferricyanide  employed  must,  of  course,  be 
perfectly  free  from  ferrocyanide :  it  may  be  tested  by  adding  a  drop  of 
ferric  chloride  solution  to  one  of  the  drops  of  ferricyanide  solution,  the  ab- 
sence of  any  resulting  blue  color  in  the  test-drops  being  proof  of  the  purity 
of  the  ferricyanide.  As  towards  the  end  of  the  operation  the  frequent  tests 
become  rather  tedious,  some  analysts  prefer  to  make  the  determinations  in 
duplicate,  using  the  first  to  get  an  approximate  result. 

When  the  ore  is  completely  decomposed  by  hydrochloric  acid,  a  sepa- 
rate treatment  of  the  residue  is  unnecessary,  and  the  ore  may  be  weighed 
at  once  into  the  flask  and  treated  with  10  c.c.  hydrochloric  acid  and  a  little 
potassium  chlorate  when  organic  matter  is  present.  When  the  ore  is  com- 
pletely decomposed,  and  any  chlorine  from  the  potassium  chlorate  driven 
off,  add  30  c.c.  of  water,  and  proceed  with  the  deoxidation. 

Instead  of  deoxidizing  the  solution  of  ferric  chloride  by  zinc,  it  may  be 
deoxidized  by  a  solution  of  ammonium  bisulphite.  In  fact,  the  deoxidation 
by  zinc  is  not  practicable  in  ores  containing  much  titanic  acid,  for  the 
titanic  acid  is  reduced  by  metallic  zinc  to  titanic  oxide,  imparting  a  purple 
or  blue  color  to  the  solution,  and  acting  like  a  solution  of  ferrous  salt  on 
the  standard  solution  of  permanganate.  In  deoxidizing  a  solution  of  ferric 
chloride  by  this  method  it  should  be  placed  in  a  flask  of  120  c.c.  capacity, 
and  two  or  three  small  spirals  of  platinum  wire  added  to  facilitate  the  sub- 
sequent boiling.  Add  cautiously  to  the  solution  (which  should  not  exceed 
40  c.c.  in  volume)  enough  ammonia  to  produce  a  slight  permanent  precipi- 
tate of  ferric  hydrate,  which  remains  even  after  vigorous  shaking.  Add 


228  ANAL  YSIS   OF  IRON  ORES. 

now  5  c.c.  of  a  strong  solution  of  ammonium  bisulphite,*  shake  vigorously, 
and  warm  the  flask  gently.  -  As  the  color  of  the  solution  (at  first  a  deep 
red)  fades,  increase  the  heat,  and  finally  heat  to  boiling.  When  the  solu- 
tion is  colorless,  add  to  it  the  solution  of  the  residue  and  10  c.c.  sulphuric 
acid  mixed  with  20  c.c.  water.  Boil  the  solution  until  all  the  sulphurous 
acid  is  driven  off.  When  the  escaping  steam  no  longer  smells  of  sul- 
phurous anhydride,  place  the  flask  in  cold  water,  wash  down  the  funnel 
and  the  neck  of  the  flask,  filling  the  latter  full  of  water,  and  when  the 
solution  is  cold  transfer  it  to  a  dish  and  titrate  with  a  standard  solution. 
A  third  method  of  deoxidizing  the  solution  of  ferric  chloride  is  used,  in 
which  the  reducing  agent  is  a  solution  of  stannous  chloride.  The  investi- 
gations of  Zimmerman  f  and  Reinhardt  \  have  made  this  method  of  reduc- 
tion a  favorite  one,  especially  when,  by  the  use  of  phosphoric  acid  and 
manganous  sulphate,  the  subsequent  titration  with  potassium  permanganate 
is  practicable.  The  details  are  as  follows.  Prepare  the  following  solutions  : 

1.  Phosphoric   acid    solution.      Dissolve   200   grammes  of  crystallized 
manganous  sulphate  in  I  litre  of  water,  add  a  few  drops  of  sulphuric  acid, 
and  filter.     Add  to  this   I    litre  of  phosphoric  acid  (1.3   sp.  gr.),  600  c.c. 
water,  and  400  c.c.  strong  sulphuric  acid. 

2.  Stannous  chloride  solution.      Dissolve  120  grammes   of  granulated 
tin,  free  from  iron,  in  500  c.c.  hydrochloric  acid  (1.19  sp.  gr.),  dilute  to  I 
litre,  and  filter  through  asbestos.     To  the  filtrate  add  I  litre  of  hydrochloric 
acid  (1.124  SP-  gr-)  and  2  litres  of  water. 

3.  Mercuric    chloride   solution.      Dissolve    50    grammes    of    mercuric 
chloride  in   I   litre  of  water  and  filter. 

Dissolve  I  gramme  of  the  ore  in  30  c.c.  strong  hydrochloric  acid  (if 
necessary,  ignite,  and  fuse  the  residue  with  a  little  sodium  carbonate,  dis- 
solve in  water  and  hydrochloric  acid,  and  add  to  the  main  solution),  transfer 
to  a  1 50  c.c.  Erlemeyer  flask,  heat  to  boiling,  and  add,  from  a  burette,  stan- 
nous chloride  solution  until  the  color  of  the  solution  fades  completely. 
Pour  into  the  dish  600  c.c.  of  water  and  add  to  it  60  c.c.  of  the  phosphoric 

*  See  page  44.  f  Berichte  d.  Chem.  Ges.,  1884,  xv.  779. 

\  Chem.  Zeit.,  xiii.  324. 


DETERMINATION  OF   TOTAL    IRON.  22$ 

acid  solution.  To  the  deoxidized  solution  in  the  flask  add  60  c.c.  of  the 
mercuric  chloride  solution,  pouring  it  all  in  at  once,  shake  vigorously  and 
wash  the  solution  out  into  the  dish,  using  plenty  of  wash-water,  and  titrate 
with  permanganate  in  the  usual  way.  The  phosphoric  acid  makes  the 
solution  nearly  colorless  by  forming  ferric  phosphate,  and  the  end  reaction 
is  very  sharp. 

The  mercuric  chloride  should  not  be  added  until  everything  is  ready  for 
the  titration,  as  the  absence  of  any  deoxidizing  substance  may  cause  the 
solution  to  become  slightly  oxidized  on  standing. 

Mixer  and  Dubois  *  give  several  modifications  of  the  method  as  used 
in  the  Lake  Superior  region.  They  employ  a  solution  of  potassium  per- 
manganate of  such  strength  that  I  c.c.  equals  2  per  cent,  of  iron  when 
.5  gramme  of  ore  is  used.  They  use  for  standardizing  the  permanganate 
an  iron  ore  the  amount  of  iron  in  which  is  accurately  known,  and  if  the 
permanganate  is  not  exactly  of  the  proper  strength,  such  a  weight  of  the 
ore  is  taken,  approximating  .5  gramme,  that  the  reading  of  the  burette 
multiplied  by  2  gives  the  percentage  of  iron.  Necessarily  this  implies 
the  use  of  the  same  weight  of  the  ore  to  be  analyzed.  They  also  add 
to  the  ore  about  2.5  c.c.  of  a  25  per  cent,  solution  of  stannous  chloride 
before  adding  the  hydrochloric  acid,  as  this  is  said  to  very  much  hasten 
the  solution  of  the  ore. 

Methods  for  Standardizing1  the  Solutions. 

It  is  of  the  utmost  importance  that  the  value  of  the  standard  solution 
employed  should  be  determined  with  the?  greatest  accuracy  if  the  results 
obtained  by  its  use  are  to  be  anything  but  mere  approximations.  To  do 
this,  not  only  should  the  reagents  employed  be  pure,  but  the  conditions 
under  which  the  standard  is  fixed  should  be,  as  nearly  as  practicable,  those 
under  which  it  is  employed  in  actual  use.  The  conditions  referred  to  are 
not  only  those  of  temperature,  dilution,  etc.,  but  of  the  actual  chemical 
composition  of  the  liquid  acted  on  by  the  standard  solution  by  which  its 
value  is  determined. 

*  Journal  of  the  American  Chem.  Soc.,  xvii.  405. 


230  ANALYSIS   OF  IRON  ORES. 

The  best  reagent  to  employ  is  a  solution  of  ferric  chloride  of  known 
strength.  To  prepare  this,  dissolve  100  grammes  of  wrought  iron  (free 
from  manganese  and  arsenic,  and  in  which  the  phosphorus  has  been 
accurately  determined)  in  nitric  acid,  evaporate  to  dryness  in  a  capsule, 
and  heat  until  the  iron  nitrate  is  largely  decomposed  and  the  mass 
separates  easily  from  the  bottom  and  sides  of  the  capsule.  Transfer  to  a 
piece  of  platinum-foil  with  the  edges  turned  up,  and  heat  for  some  time 
in  a  muffle  at  a  very  high  temperature,  or  heat  it,  a  portion  at  a  time,  in  a 
crucible  at  the  highest  temperature  obtainable  by  a  blast-lamp.  Grind 
the  entire  mass  very  fine  in  an  agate  mortar,  dissolve  in  hydrochloric  acid, 
evaporate  to  dryness,  redissolve  in  dilute  hydrochloric  acid,  filter  to  get 
rid  of  silica,  and  dilute  the  solution  to  about  4  litres.  20  c.c.  of  this 
solution  will  contain  about  .5  gramme  iron,  and  it  may  be  kept  indefinitely 
in  a  glass-stoppered  bottle  sealed  with  paraffine,  or  after  being  thoroughly 
mixed  it  may  be  preserved  in  a  number  of  smaller  bottles  properly  secured. 

Wash  out  and  dry  thoroughly  three  of  the  small  flasks  used  for 
deoxidizing  the  solutions  of  the  ores,  weigh  them  to  within  I  mg.,  and 
measure  into  each  a  portion  of  the  ferric  chloride  solution  ranging  from 
15  to  25  c.c.  in  volume.  Weigh  the  flasks  and  their  contents;  the 
differences  between  the  first  and  second  weights  are  the  weights  of  the 
ferric  chloride  solution  taken.  Transfer  the  solution  carefully  from  each 
flask  to  a  platinum  dish,  dilute,  boil,  precipitate  by  ammonia,  filter,  wash, 
dry,  ignite,  and  weigh  the  precipitate  with  the  precautions  mentioned 
farther  on.  The  precipitate  is  ferric  oxide  -f-  phosphoric  acid.  Subtract 
from  this  weight  the  amount  of  phosphoric  acid  in  this  weight  of  the 
material,  and  the  remainder  will  be  the  weight  of  ferric  oxide  in  the 
amount  of  solution  used.  Suppose,  for  example,  that  the  original  iron 
contained  .1  per  cent,  phosphorus,  this  would  be  equivalent  to  0.229  per 
cent,  phosphoric  acid,  but,  as  the  iron  has  been  oxidized  to  ferric  oxide, 
the  percentage  of  phosphoric  acid  in  the  iron  as  oxide  would  be  only  -£-$ 
as  great  as  in  the  iron  itself,  the  weight  as  oxide  being  -ty1  as  great  as  it 
was  as  iron.  Therefore  multiply  .229  per  cent,  by  .7  for  the  percentage 
of  phosphoric  acid  in  the  ferric  oxide,  which  gives  .16  per  cent,  phosphoric 
acid.  If  we  further  suppose  that  the  weight  of  ferric  oxide  -f-  phosphoric 


DETERMINATION  OF   TOTAL    IRON.  2$  I 

acid  obtained  was  .8131  gramme,  .16  per  cent,  of  this  would  be  .0013 
gramme,  the  weight  of  phosphoric  acid  in  the  precipitate,  and  .8131  - 
.0013  —  .81 1 8  gramme,  the  weight  of  ferric  oxide  in  the  amount  of  solution 
taken.  Divide  this  weight  by  the  weight  of  the  solution,  and  the  result 
is  the  weight  of  ferric  oxide  in  I  gramme  of  the  solution  of  ferric  chloride. 
Take  the  mean  of  the  three  results  obtained  in  this  way,  and  call  this 
result  the  value  of  the  ferric  chloride  solution  in  ferric  oxide,  or  multiply 
by  .7  for  its  value  in  iron. 

To  standardize  the  permanganate  or  bichromate  solution,  weigh  out 
three  portions  of  the  ferric  chloride  solution  into  the  flasks,  reduce  them 
by  the  method  selected,  and  titrate  the  reduced  solutions  exactly  as 
directed  above.  Before  calculating  the  strength  of  the  standard  solution 
a  small  correction  must  be  applied  to  the  burette  reading,  due  to  the 
fact  that  a  definite  amount  of  oxidizing  solution  is  required  to  produce 
the  end  reaction  in  all  cases  where  permanganate  is  used,  and,  when 
bichromate  is  used,  in  those  cases  where  zinc  has  been  the  deoxidizing 
agent. 

Treat  3  grammes  of  zinc  in  a  small  flask  with  5  c.c.  hydrochloric  acid 
and  20  c.c.  water,  add  gradually  10  c.c.  sulphuric  acid  and  20  c.c. 
water.  When  the  zinc  has  all  dissolved,  place  the  flask  in  cold,  water 
until  the  solution  is  cold.  Wash  it  out  into  the  dish,  dilute  to  I  litre, 
add  20  c.c.  ferric  chloride  solution  (free  from  ferrous  salt),  and  drop  in  the 
standard  solution  until  the  end  reaction  is  obtained.  Subtract  the  cor- 
rection thus  obtained  from  every  burette  reading.  To  calculate  the 
strength  of  the  standard  solution,  therefore,  subtract  the  correction  from 
the  burette  reading,  and  the  result  is  the  absolute  volume  of  the  standard 
solution  required  to  oxidize  the  ferrous  salt  in  the  solution  operated  on. 
Knowing  then  the  weight  of  the  ferric  chloride  solution  used,  the  amount 
of  iron  in  each  gramme  of  the  solution,  and  the  volume  of  the  standard 
required  to  oxidize  this  amount,  the  value  of  each  c.c.  of  the  standard 
solution  is  found  by  multiplying  the  weight  of  ferric  chloride  solution  used 
by  the  value  of  each  gramme  in  iron,  and  dividing  the  amount  by  the 
number  of  c.c.  of  the  standard  used  in  titrating.  The  mean  of  the  results 
obtained  in  the  three  portions  used  should  be  taken  as  the  value  of  the 


232  ANALYSIS    OF  IRO^T  ORES. 

standard  solution.  An  example  will  illustrate  the  method  of  computation, 
and,  as  logarithms  very  much  facilitate  these  calculations,  they  will  be 
given  in  the  example  as  well. 

\Veightofemptyflask    ...................  22.8817 

Weight  of  flask  -f-  ferric  chloride  solution    ...........  40.0640 


Weight  of  ferric  chloride  solution  used     ............  I7.i823  =  log.  1.2350813 

Value  of  ferric  chloride  solution,  determined  as 

on  p.  230      ...........  I  gramme  =  .03227  gramme  iron  =  log.  8.5087990  —  10 

Iron  in  ferric  chloride  solution  used    ...........  5544-8  gramme  =  log.  9.7438803—  10 

Burette  reading  after  titration     .    ............     :=  82.0    c.c. 

Less  correction     .....................    0.25 

Corrected  reading    ...    ................      81.75  C.c.  =  ^°S-  I  -9  '24878 

I  c.c.  standard  solution  —  .0067826  gramme  iron    ...........  —  log.  7.8313925  —  10 

Of  course  in  calculating  the  amount  of  iron  in  an  ore  it  is  only  neces- 
sary to  get  the  logarithm  of  the  corrected  reading  (page  231)  and  add 
it  to  the  logarithm  of  the  standard  solution  as  found  above,  the  number 
corresponding  to  the  resulting  logarithm  being  the  weight  of  iron  in 
grammes  in  the  ore.  This  multiplied  by  100  will  give  the  percentage. 

Very  fine  iron  wire  may  be  used  to  standardize  the  solutions  instead 
of  a  standard  solution  of  ferric  chloride.  Weigh  into  the  reducing 
flasks  from  .4  to  .6  gramme  of  fine  iron  wire  (page  55)  which  has  been 
carefully  rubbed  with  fine  sand-paper  and  wiped  clean  with  a  linen  rag. 
Dissolve  in  10  c.c.  hydrochloric  acid  and  20  c.c.  water,  with  the  addition 
of  a  few  small  crystals  of  potassium  chlorate.  Deoxidize  carefully,  and 
titrate  as  before  directed.  Multiply  the  weight  of  iron  wire  by  .998  to 
get  the  absolute  amount  of  iron  used,  apply  the  proper  correction  to  the 
burette  reading,  and  calculate  the  value  of  the  standard. 

Ferrous  sulphate,  FeSO4,7H2O,*  containing  20.1439  per  cent,  iron,  or  the 
ferrous-ammonium  sulphate,  FeSO4,(NH4)2SO4,6H2O,t  containing  14.2857 
per  cent.,  or  almost  exactly  one-seventh  of  its  weight  of  iron,  may  be  used 
instead  of  ferric  chloride  solution  or  iron  wire  to  determine  the  value 
of  the  standard  solutions.  The  pure  salts  are  generally  weighed  ofF,  dis- 

*  See  page  56.  f  See  page  56. 


DETERMINATION  OF  FERROUS   OXIDE.  233 

solved  in  water  with  10  c.c.  sulphuric  acid  added,  and  titrated  direct, 
but  they  are  not  so  satisfactory  in  use  as  the  first  and  second  methods 
described.  It  is  important  to  have  the  standard  solutions  of  the  proper 
strength, — that  is,  neither  too  dilute  nor  too  concentrated  for  convenience 
in  working.  As  iron  ores  rarely  contain  more  than  60  per  cent,  metallic 
iron,  a  standard  solution  100  c.c.  of  which  are  equal  to  .66  gramme  iron 
will  be  found  sufficiently  concentrated  to  avoid  the  necessity  of  refilling 
the  burette  for  a  determination ;  and  where  ores  much  poorer  than  this 
are  habitually  used  the  solutions  may  be  correspondingly  more  dilute. 

When  potassium  permanganate  is  added  to  a  solution  of  ferrous  sul- 
phate the  reaction  is  lo.FeSO,  -f  2KMnO4  +  8H2SO4  =  5Fe2(SOJ3  -f  K2SO4 
-j-  2MnSO4  -f-  8H2O,  or  316.2  parts  by  weight  of  potassium  permanganate 
will  oxidize  560  parts  by  weight  of  iron,  or  3.727  grammes  potassium 
permanganate  to  the  litre  will  give  a  solution  of  about  the  strength  required. 

In  the  case  of  potassium  bichromate  the  reaction  is  6FeSO4  +  K2Cr2O7 
+  7H2S04^3Fe2(SOJ3+K2S04  +  Cr2(S04)3  +  7H20,  or  294.5  parts  by 
weight  of  potassium  bichromate  will  oxidize  336  parts  of  iron,  or  5.785 
grammes  of  potassium  bichromate  dissolved  in  I  litre  of  water  will  give 
a  solution  100  c.c.  of  which  will  be  equivalent  to  about  .66  gramme  iron. 

To  prepare  the  solutions,  therefore,  dissolve  the  above  weights,  or 
multiples  of  them,  in  pure  distilled  water,  allow  the  solution  to  stand 
for  some  little  time,  filter  through  asbestos,  and  dilute  to  the  proper 
volume.  Mix  thoroughly  by  shaking  in  the  bottle,  and  standardize  as 
above  directed.  The  solutions  should  be  kept  in  glass-stoppered  bottles 
in  a  dark  closet,  and  the  bottles  should  be  well  shaken  whenever  the 
solution  is  used. 


DETERMINATION    OF    IRON    EXISTING  AS    FERROUS 

OXIDE. 

Many  iron  ores  contain  iron  in  the  state  of  ferrous  oxide,  and 
this  may  be  either  soluble  or  insoluble  in  hydrochloric  acid.  To  de- 
termine the  ferrous  oxide  soluble  in  hydrochloric  acid,  weigh  i  gramme 
of  the  finely  ground  ore  into  the  flask  A,  Fig.  96,  of  about  100  c.c. 


234 


ANALYSIS    OF  IRON  ORES. 


capacity.  Close  the  flask  with  a  rubber  stopper  fitted  with  the  two 
glass  tubes  B  and  C,  and  place  it  in  the  position  shown  in  the  sketch. 
Connect  the  tube  C  by  means  of  a  piece  of  rubber  tubing  with  the  bent 
tube  D  dipping  below  the  surface  of  the  water  in  the  beaker  E.  Pass 
a  current  of  carbonic  acid  through  the  tube  B  until  all  the  air  is  ex- 


FIG.  96. 


CO- 


Q 


pelled,  then  remove  for  a  moment  the  rubber  tube  connecting  B  with  the 
source  of  carbonic  acid,  and  by  means  of  a  small  funnel  and  rubber 
tube  introduce  into  the  flask  A,  through  B,  from  10  to  12  c.c.  strong 
hydrochloric  acid,  and  establish  the  current  of  carbonic  acid  as  before. 
Heat  the  flask  carefully,  and  when  the  ore  is  entirely  decomposed,  or  the 


DETERMINATION  OF  FERROUS    OXIDE. 


235 


hydrochloric  acid  ceases  to  exert  any  further  action  on  it,  remove  the 
source  of  heat,  stop  the  current  of  carbonic  acid  for  a  moment,  cool  the 
flask  with  the  hand,  and  allow  the  partial  vacuum  thus  formed  to  draw 
the  water  from  E  back  into  A.  Turn  on  the  current  of  carbonic  acid 
again,  place  a  dish  of  cold  water  under  the  flask  A,  and  allow  the  solution 


FIG.  97. 


NCHES 


to  cool.  Dissolve  in  a  small  flask  3  grammes  of  metallic  zinc  in  10  or 
15  c.c.  sulphuric  acid,  diluted  with  the  proper  quantity  of  water,  cool  it, 
and  have  it  ready  to  pour  into  the  titrating-dish  by  the  time  the  solu- 
tion in  the  flask  A  is  cool.  Wash  the  solution  of  the  ore  from  the 
flask  A  into  the  dish,  add  the  zinc  solution,  dilute  to  I  litre,  and  titrate 
with  a  standard  solution.  Subtract  from  the  burette  reading  the  proper 


236  ANALYSIS   OF  IRON  ORES. 

correction,  calculate  the  percentage  of  iron,  divide  by  7,  and  multiply  by 
9.  The  result  is  the  percentage  of  ferrous  oxide  in  the  ore  soluble  in 
hydrochloric  acid.  Allow  the  solution  in  the  dish  to  stand  for  a  few 
minutes,  when  all  the  undecomposed  particles  of  ore  will  settle.  Draw 
off  the  greater  part  of  the  clear  supernatant  fluid  with  a  siphon,  wash 
the  sediment  into  a  beaker  with  a  jet  of  cold  water,  filter  on  a  thin  felt  * 
in  a  Gooch  crucible,  and  wash  the  sediment  on  the  felt  with  cold  water. 
Transfer  the  felt  and  sediment  to  a  platinum  crucible,  pour  into  the  cruci- 
ble from  5  to  10  c.c.  of  hydrochloric  acid  and  about  half  the  quantity  of 
hydrofluoric  acid,  cover  the  crucible,  and  place  it  in  the  water-bath  shown 
in  Fig.  97.  The  crucible  rests  on  a  platinum  triangle  fixed  over  the  hole 
in  the  centre  of  the  top  of  the  bath.  Around  this  hole  is  a  groove  in 
which  a  funnel  stands  as  shown  in  the  cut,  while  the  water  in  the  groove 
forms  a  tight  joint. f  Pass  a  current  of  carbonic  acid  or  coal-gas  through 
the  tube  in  the  side  of  the  bath,  as  figured  in  the  cut,  to  exclude  the 
air,  and  heat  the  bath  until  the  residue  and  felt  are  completely  dissolved. 
Wash  the  crucible  out  into  the  titrating-dish  into  which  have  been 
poured  just  previously  3  grammes  of  zinc  dissolved  in  sulphuric  acid 
and  enough  cold  water  to  make  the  solution  up  to  nearly  I  litre. 
Titrate,  and  calculate  the  amount  of  ferrous  oxide  as  before. 

Of  course  separate  portions  of  the  ore  may  be  used  to  determine  the 
ferrous  oxide  soluble  and  insoluble  in  hydrochloric  acid,  but  it  is  more 
troublesome,  and  experience  has  shown  that  it  is  no  more  accurate,  and  in 
some  cases  less  accurate,  than  the  method  just  described. 

The  total  ferrous  oxide  may  also  be  determined  in  one  operation  by 
treating  I  gramme  of  the  ore  direct  in  the  crucible  with  20  c.c.  hydrochloric 
acid  and  20  c.c.  hydrofluoric  acid,  but  it  is  often  difficult  to  get  the  ore 
perfectly  dissolved  even  by  prolonged  heating  in  the  bath,  and  the  ore 
must  be  ground  very  fine  in  the  agate  mortar.  It  is  necessary  to  remove 
the  funnel  from  time  to  time,  raise  the  lid  of  the  crucible,  and  stir  the 
contents  with  a  platinum  wire. 


*  The  asbestos  of  which  the  felt  is  made  must  be  free  from  ferrous  oxide. 

f  Avery,  Chem.  News,  xix.  270  ;  Wilbur  and  Whittlesay,  Crook's  Select  Methods,  p.  133. 


DETERMINATION  OF  SULPHUR.  237 

When  the  ore  is  completely  decomposed  by  hydrochloric  acid,  or  when 
the  portion  undecomposed  contains  no  ferrous  oxide,  the  treatment  of 
the  residue  is  unnecessary. 

When  an  ore  contains  much  organic  matter,  an  accurate  determination 
of  ferrous  oxide  is  often  impossible,  as  the  solution  of  the  ore  in  hydro- 
chloric acid  reduces  some  of  the  ferric  salt. 


DETERMINATION    OF   SULPHUR. 

Sulphur  exists  in  two  conditions  in  iron  ores,  as  sulphur  in  the  form 
of  sulphides  and  as  sulphuric  acid  in  the  form  of  sulphates.  To  determine 
the  total  sulphur,  weigh  I  gramme  of  the  finely  ground  ore  into  a  large 
platinum  crucible,  add  to  it  10  grammes  of  sodium  carbonate  and  a  little 
potassium  nitrate  (less  than  I  gramme  *).  Mix  thoroughly  with  a  platinum 
wire,  and  heat  carefully  over  a  large  alcohol  lamp  until  the  mass  appears 
perfectly  liquid  and  in  a  tranquil  state  of  fusion.  Run  the  fusion  well 
up  on  the  sides  of  the  crucible,  allow  it  to  cool,  and  treat  it  in  the 
crucible  with  boiling  water.  Pour  the  liquid  into  a  tall,  narrow  beaker, 
treat  the  crucible  again  with  boiling  water,  and  repeat  the  operation  until 
all  the  sodium  salts  are  dissolved  and  nothing  remains  in  the  crucible 
except  the  unavoidable  stains.  Stir  the  liquid  in  the  beaker  well  and  allow 
the  iron  oxide  to  settle.  If  the  solution  is  colored  red  or  green,  it  is 
proof  of  the  presence  of  manganese  in  the  ore ;  add  a  few  drops  of 
alcohol,  which  will  precipitate  the  manganese  as  oxide,  leaving  the  solution 
colorless  unless  the  ore  contains  chromium,  in  which  case  the  solution 
will  be  yellowish.  Decant  the  supernatant  liquid  on  a  small  filter,  allow- 
ing the  filtrate  to  run  into  a  No.  4  beaker,  fill  the  small  beaker  nearly 
full  of  hot  water,  stir  well,  and  allow  to  settle.  Decant  again  on  the  filter, 
and  repeat  the  operation  once  more.  Acidulate  the  collected  filtrates  with 
hydrochloric  acid  (about  20  c.c.  will  be  required),  evaporate  to  dryness 
in  the  air-bath,  redissolve  in  water  with  a  few  drops  of  hydrochloric  acid, 

*  See  pages  46  and  48.  It  is  well  to  make  a  blank  determination,  using  the  same  amounts 
of  sodium  carbonate,  potassium  nitrate,  and  hydrochloric  acid,  applying  the  amount  of  barium 
sulphate  found  as  a  correction. 


238  ANALYSIS   OF  IRON  ORES. 

filter  into  a  No.  3  beaker,  heat  the  filtrate  to  boiling,  and  add  10  c.c.  of  a 
boiling  solution  of  barium  chloride.*  Allow  to  stand  for  some  hours, 
filter  on  a  Gooch  crucible  or  on  a  small  ashless  filter,  ignite,  and  weigh 
as  barium  sulphate,  which  multiplied  by  .1376  gives  the  weight  of  sulphur. 
The  insoluble  portion  from  the  aqueous  solution  of  the  fusion  may  be 
used  to  determine  the  total  iron  in  the  ore,  and  is  very  convenient  for  this 
purpose  in  ores  difficult  to  dissolve.  Pour  into  the  crucible  in  which  the 
fusion  was  made  about  10  c.c.  of  hydrochloric  acid,  place  the  lid  on  the 
crucible,  and  warm  slightly  to  dissolve  the  adhering  oxides,  dilute  with  an 
equal  bulk  of  water,  and  pour  it  on  the  small  filter  through  which  the 
aqueous  solution  was  decanted,  allowing  it  to  run  into  the  beaker  which 
contains  the  residue  of  iron  oxide,  etc.  Wash  out  the  crucible,  pouring 
the  washings  on  the  filter,  and  wash  the  filter  free  from  ferric  chloride  with 
a  jet  of  cold  water.  Evaporate  the  solution  in  the  beaker  to  dryness,  redis- 
solve  in  10  c.c.  hydrochloric  acid,  and  transfer  the  solution  of  ferric  chloride, 
the  silica,  etc.,  to  one  of  the  small  flasks,  deoxidize,  and  titrate  as  directed. 

The  sulphur  which  exists  as  sulphuric  acid  in  an  iron  ore  is  usually 
combined  with  either  calcium  or  barium :  as  calcium  sulphate  or  of  any 
of  the  other  alkaline  earths  except  barium,  of  the  alkalies,  or  of  the  metals, 
it  is  soluble  in  hydrochloric  acid ;  as  barium  sulphate  it  is  practically 
insoluble.  We  may,  therefore,  determine  the  soluble  sulphates  as  follows. 
Boil  10  grammes  of  the  ore  with  30  c.c.  hydrochloric  acid  and  60  c.c.  water, 
filter  from  the  mass  of  the  undissolved  ore,  evaporate  the  filtrate  to  dryness, 
redissolve  in  hydrochloric  acid  and  water  (i  to  2),  filter  into  a  No.  2  beaker, 
nearly  neutralize  by  ammonia,  heat  to  boiling,  and  precipitate  by  barium 
chloride  solution.  Filter  and  wash  the  precipitate,  ignite  and  weigh  as 
barium  sulphate,  which  contains  34.352  per  cent,  sulphuric  anhydride. 

To  determine  the  sulphuric  acid  which  exists  as  barium  sulphate,  treat 
10  grammes  of  the  ore  with  50  c.c.  hydrochloric  acid  until  the  ore  appears 
to  be  decomposed.  Evaporate  to  dryness,  redissolve  in  dilute  hydrochloric 
acid  (i  to  3),  dilute,  filter,  and  wash  the  insoluble  matter  thoroughly.  Ignite 
and  fuse  the  insoluble  matter  with  sodium  carbonate,  treat  the  fused  mass 

*  See  page  51. 


DETERMINATION  OF  PHOSPHORIC  ACID.  239 

with  hot  water,  and  filter.  In  the  filtrate  is  the  sulphuric  acid  as  sodium 
sulphate,  while  the  barium  remains  on  the  filter  as  barium  carbonate.  It 
is  safer  to  calculate  the  barium  sulphate  from  the  amount  of  barium  rather 
than  from  the  amount  of  sulphuric  acid,  as  the  ore  may  contain  sulphides 
(pyrites,  etc.)  which  are  not  decomposed  by  hydrochloric  acid,  but  are 
decomposed  and  partly  oxidized  by  fusion  with  sodium  carbonate.  The 
other  forms  of  barium  besides  the  sulphate  (silicate  and  carbonate)  are 
readily  decomposed  by  hydrochloric  acid,  and  are  not  likely  to  be  found 
with  the  barium  in  the  insoluble  residue.  It  is,  of  course,  possible  to 
suppose  the  coexistence  of  barium  silicate  or  carbonate  and  of  calcium 
sulphate  in  an  ore,  and  the  consequent  formation  of  barium  sulphate  when 
the  ore  is  decomposed  by  hydrochloric  acid ;  but,  as  the  soluble  sulphuric 
acid  is  determined  in  one  operation  and  the  insoluble  in  another,*  the  total 
amount  of  sulphuric  acid  existing  as  such  is  determined  and  the  object  of 
the  analysis  attained.  To  determine  the  barium,  then,  treat  the  insoluble 
matter  obtained  by  the  filtration  of  the  aqueous  solution  of  the  fusion  by 
dilute  hydrochloric  acid,  evaporate  to  dryness  to  render  the  silica  insoluble, 
redissolve  in  water  with  a  few  drops  of  hydrochloric  acid,  filter  into  a  No.  2 
beaker,  heat  the  filtrate  to  boiling,  and  add  a  few  drops  of  sulphuric  acid 
diluted  with  a  little  water.  Allow  the  precipitate  to  settle,  filter,  wash,  ignite, 
and  weigh  as  barium  sulphate,  from  which  weight  calculate  the  amount  of 
sulphuric  anhydride  in  the  ore  insoluble  in  hydrochloric  acid.  To  find  the 
amount  of  sulphur  existing  as  sulphides,  subtract  from  the  total  sulphur 
the  amount  of  sulphur  in  the  sulphuric  anhydride  found  as  sulphates. 


DETERMINATION    OF    PHOSPHORIC    ACID. 

Treat  5  or  10  grammes  of  the  finely  ground  ore  in  30  or  60  c.c.  hydro- 
chloric acid.  (With  low  phosphorus  ores  use  10  grammes;  with  others,  5 
grammes.)  When  the  ore  is  decomposed,  evaporate  to  dryness,  redissolve 
in  20  or  40  c.c.  hydrochloric  acid,  dilute,  filter,  and  proceed  exactly  as 

*  The  insoluble  matter  from  the  treatment  of  10  grammes  of  the  ore  with  hydrochloric  acid 
for  the  determination  of  soluble  sulphates  (page  238)  may  be  used  to  determine  the  barium  sulphate. 


240  ANAL  YSIS   OF  IRON  ORES. 

directed  in  the  determination  of  phosphorus  in  iron  and  steel  (page  80 
et  seg.).  The  weight  of  the  magnesium  pyrophosphate  multiplied  by 
.63788  gives  the  weight  of  the  phosphoric  acid.  The  weight  of  the 
ammonium  phospho-molybdate  multiplied  by  .03735  gives  the  weight  of 
the  phosphoric  acid. 

Titanic  acid  is  very  generally  found  associated  with  iron  ores,  and  may 
be  regarded  as  one  of  the  usual  constituents.  As  mentioned  on  page 
85,  its  presence,  if  overlooked,  may  lead  to  serious  errors  in  the  determi- 
nation of  phosphoric  acid.  When  an  ore  contains  much  titanic  acid  it 
may  readily  be  recognized  by  the  peculiar  milky  appearance  of  the  solu- 
tion when  it  is  diluted  preparatory  to  filtering  off  the  insoluble  matter, 
and  by  the  strong  tendency  it  shows  to  run  through  the  filter  as  soon  as 
the  attempt  is  made  to  wash  the  insoluble  matter  with  water.  Smaller 
quantities  of  titanic  acid  may  be  recognized  by  the  clouding  of  the  solution 
when  it  is  deoxidized  by  ammonium  bisulphite,  as  noted  on  page  88. 
In  the  latter  case,  however,  this  clouding  may  be  caused  by  the  formation 
of  barium  sulphate  when  the  ore  contains  the  latter  element  in  the  form 
of  carbonate  or  silicate.  Under  these  circumstances  silica  in  the  solution 
may  also  cause  a  cloud  which  closely  resembles  that  of  titanic  acid,  while 
barium  sulphate  may  readily  be  distinguished  from  either  by  its  granular 
appearance  and  its  tendency  to  settle  to  the  bottom  of  the  beaker. 

The  insoluble  residue  from  the  solution  of  the  ore  in  hydrochloric 
acid  should,  therefore,  be  treated  to  recover  any  phosphoric  acid  which 
may  have  remained  insoluble  in  combination  with  titanic  acid.*  An  addi- 
tional test  for  the  presence  of  titanic  acid,  and  one  that  rarely  fails  even 
with  very  small  amounts,  is  to  dissolve  the  insoluble  matter  from  the 
aqueous  solution  of  the  fusion  of  the  residue  from  the  hydrofluoric  acid 
and  sulphuric  acid  treatment  of  the  insoluble  portion  of  the  ore  in  dilute 
hydrochloric  acid,  allowing  it  to  run  into  a  test-tube  and  adding  metallic 


*  When  hydrofluoric  acid  is  not  available,  fuse  the  residue  with  sodium  carbonate,  treat  the 
fused  mass  with  hot  water,  filter,  acidulate  the  filtrate  with  hydrochloric  acid,  and  evaporate  to 
dryness  to  render  the  silica  insoluble.  Redissolve  in  water  with  a  little  hydrochloric  acid,  filter, 
add  a  little  ferric  chloride,  and  make  a  separate  acetate  precipitation  in  this  portion,  adding  the 
solution  to  the  solution  of  the  main  acetate  precipitation. 


DETERMINATION  OF   TITANIC  ACID.  241 

zinc.  When  titanic  acid  is  present  the  solution  first  becomes  colorless, 
then  pink  or  purple,  and  finally  blue  from  the  formation  of  titanic  oxide. 
The  simplest  way  is  to  proceed  as  directed  on  pages  87  and  88  when 
using  the  acetate  method,  or  on  page  92  when  using  the  molybdate 
method.  These  methods  are  not  practicable,  however,  when  the  ore  con- 
tains a  very  large  amount  of  titanic  acid,  and  recourse  must  be  had  to  the 
method  described  on  page  85,  involving  the  fusion  of  the  acetate  precipi- 
tate and  the  residue  from  the  treatment  of  the  insoluble  matter  with  hydro- 
fluoric and  sulphuric  acids,  with  sodium  carbonate  and  a  little  sodium 
nitrate.  At  any  rate,  it  is  best  to  pursue  this  method  whenever  titanic  acid 
is  also  to  be  determined,  as  the  same  portion  can  be  used  for  the  estimation 
of  both  titanic  acid  and  phosphoric  acid,  and  the  aggregate  labor  involved 
is  much  lessened. 


DETERMINATION    OF   TITANIC    ACID. 

The  determination  of  titanic  acid  has  always  presented  many  difficulties, 
and  its  separation  from  a  large  amount  of  ferric  oxide  and  alumina  has 
been  far  from  satisfactory,  besides  being  most  tedious.  The  principal 
sources  of  error  in  the  estimation  of  titanic  acid  in  iron  ores  are  the 
tendency  of  phosphoric  acid  to  prevent  the  precipitation  of  titanic  acid  by 
boiling  when  its  sulphuric  acid  solution  contains  phosphoric  acid  and  fer- 
rous sulphate,  and  the  liability  of  alumina  to  separate  out  with  the  titanic 
acid  when  the  latter  is  precipitated  under  the  circumstances  above  men- 
tioned. There  is  also  a  mechanical  difficulty,  caused  by  the  adhesion  of 
the  precipitated  titanic  acid  to  the  bottom  and  sides  of  the  beaker,  from 
which  it  can  sometimes  be  removed  only  by  boiling  with  a  strong  solution 
of  caustic  potash.  The  admirable  series  of  experiments  carried  out  by 
Dr.  Gooch  *  on  the  separation  of  aluminum  and  titanium  suggests  a  method 
which  renders  the  determination  of  titanic  acid  in  iron  ores  much  less 
troublesome,  while  adding  greatly  to  the  accuracy  of  the  results.  In  car- 
rying out  the  details  of  the  method,  dissolve  5  or  10  grammes  of  the  ore 
in  hydrochloric  acid,  and  proceed  exactly  as  in  the  determination  of  phos- 


242  AXAL  YSIS    OF  IRON  ORES. 

phoric  acid,  by  fusing  the  residue  from  the  treatment  of  the  insoluble  mat- 
ter by  hydrofluoric  and  sulphuric  acids  and  the  acetate  precipitate  with 
sodium  carbonate  and  a  little  sodium  nitrate,*  and  then  complete  the 
operation  exactly  as  described  in  the  determination  of  titanium  in  pig- 
iron.f 

The  essential  points  in  this  method  are:  i.  Separation  of  the  titanic 
acid  from  the  mass  of  ferric  oxide  by  ammonium  acetate  in  the  deoxidized 
solution.  2.  Separation  from  all  the  phosphoric  acid  and  the  greater  part 
of  the  alumina  by  fusion  with  sodium  carbonate,  by  which  means  a  so- 
dium titanate  insoluble  in  water  is  formed,  and  at  the  same  time  sodium 
phosphate  and  aluminate  soluble  in  that  menstruum.  3.  Separation  of 
the  last  traces  of  alumina  from  the  ferric  oxide,  lime,  etc.,  by  precipitating 
the  titanic  acid  in  the  thoroughly  deoxidized  solution  in  the  presence  of  a 
large  excess  of  acetic  acid  and  some  sulphurous  acid,  the  sulphuric  acid 
being  all  in  the  form  of  sodium  sulphate.  The  addition  of  a  large  excess 
of  sodium  acetate,  by  which  this  latter  condition  is  effected,  converts  all 
the  sulphate  into  acetates,  and  precipitates  the  titanic  acid  almost  instantane- 
ously as  a  hydrate,  which  is  flocculent,  settles  quickly,  shows  no  tendency 
to  run  through  the  filter,  and  is  washed  with  the  greatest  ease.  It  some- 
times happens  that  a  little  ferrous  oxide  is  precipitated  with  the  titanic  acid, 
and  the  latter,  after  ignition,  appears  discolored ;  in  this  case  fuse  with  a 
little  sodium  carbonate,  add  sulphuric  acid  to  the  cold  fused  mass,  dissolve, 
and  repeat  the  precipitation  with  sodium  acetate  in  the  presence  of  sul- 
phurous and  acetic  acids  exactly  as  in  the  first  instance. 

A  number  of  experiments  covering  all  the  points  involved  in  this 
method  show  it  to  be  extremely  accurate  and  entirely  trustworthy. 


DETERMINATION    OF    MANGANESE. 

When  manganese  alone  is  to  be  determined  in  an  ore,  any  one  of  the 
methods  described  under  the  determination  of  manganese  in  iron  and  steel 
(page  1 08)  may  be  used.  The  most  convenient,  however,  is  Ford's  method 

*  See  page  47.  f  See  page  184. 


DETERMINATION  OF  MANGANESE.  243 

with  the  modifications  necessary  in  the  analysis  of  pig-iron  (page  115). 
The  only  change  requisite  is  to  evaporate  the  solution  in  hydrochloric 
acid  to  dryness  to  render  silica  insoluble  before  filtering  off  the  insoluble 
matter. 

In  the  determination  of  manganese  in  high  grade  manganese  ores  it  is 
best  to  use  a  one-tenth  factor  weight  (0.3874  gramme)  of  the  sample,  dis- 
solve in  hydrochloric  acid,  evaporate  to  dryness,  redissolve  in  dilute  hydro- 
chloric acid,  and  filter  off  the  insoluble  matter.  Ignite  the  insoluble  matter 
in  a  platinum  crucible,  fuse  with  a  little  sodium  carbonate,  dissolve  in  water, 
acidulate  with  hydrochloric  acid,  and  evaporate  to  dryness.  Redissolve  in 
dilute  hydrochloric  acid  and  filter  into  the  main  solution.  Or,  treat  the 
ignited  insoluble  matter  with  sulphuric  and  hydrofluoric  acids,  drive  off  the 
hydrofluoric  and  the  excess  of  sulphuric,  cool,  add  water  and  a  little  hydro- 
chloric acid,  and  heat  until  the  residue  dissolves,  then  add  the  solution  to 
the  main  solution  of  the  ore. 

Evaporate  the  main  solution  until  it  is  syrupy,  add  an  excess  of  strong 
nitric  acid  and  evaporate  off  the  hydrochloric  acid.  Precipitate  by  potas- 
sium chlorate  in  the  usual  way  and  filter  through  asbestos.  Wash  the  pre- 
cipitate thoroughly  with  cold  water  to  get  rid  of  the  calcium  nitrate,  which, 
being  practically  insoluble  in  strong  nitric  acid,  will  remain  with  the  pre- 
cipitated manganese  dioxide  unless  this  precaution  be  observed.  There  is 
no  danger  of  dissolving  the  manganese  dioxide  by  this  treatment. 

Proceed  with  the  determination  as  directed  on  page  113.  Each  milli- 
gramme of  manganese  pyrophosphate  is  a  tenth  of  one  per  cent,  of  manga- 
nese in  the  ore. 

In  using  the  acetate  method  it  is,  of  course,  necessary  that  all  the  iron 
should  be  in  the  form  of  ferric  chloride,  and  also  that  there  should  be  no 
reducing  agent  in  the  solution.  Even  a  very  small  amount  of  ferrous 
chloride  will  cause  the  formation  of  a  "  brick-dust"  precipitate,  which  can- 
not be  kept  from  passing  the  filter  while  some  of  the  iron  remains  dis- 
solved in  the  acetate  solution.  When,  therefore,  the  ore  contains  ferrous 
oxide,  it  should  be  oxidized  by  nitric  acid  or  potassium  chlorate,  and  the 
excess  of  the  oxidizing  agent  removed  by  evaporation  with  hydrochloric 
acid. 


244  ANAL  YSIS    OF  IROX  ORES. 

Volhard's  Method  applied  to  High  Grade  Manganese  Ores. 

Volhard's  is  the  most  satisfactory  volumetric  method  for  high  grade 
manganese  ores.  Dissolve  I  gramme  of  the  ore  in  a  small  beaker  in 
hydrochloric  acid,  heat  until  the  chlorine  is  all  driven  off,  wash  out  into  a 
platinum  dish  (Fig.  36),  and  add  5  c.c.  strong  sulphuric  acid  and  a  little 
hydrofluoric  acid.  Evaporate  to  dry  ness  and  heat  until  the  sulphuric  acid 
begins  to  volatilize.  Cool,  dissolve  in  water,  transfer  to  a  300  c.c.  flask,  and 
proceed  as  directed  on  page  1 16,  except  that  100  c.c.  of  the  filtered  solu- 
tion represents  one-third  if  a  gramme  of  the  ore  is  used. 

It  is  necessary  to  heat  the  solution  in  the  flask  after  there  appears  to 
be  a  slight  excess  of  permanganate.  This  will  make  the  precipitate  settle 
rapidly  and  generally  show  the  necessity  for  adding  more  permanganate. 

A  large  number  of  comparative  analyses  have  shown  that  it  is  necessary 
to  add  one  one-hundredth  of  the  amount  obtained  to  get  the  true  percentage 
of  manganese;  in  other  words,  the  results  obtained  are  always  one  one- 
hundredth  too  low. 

For  instance,  if  by  calculation  the  ore  contains  50  per  cent,  of  manga- 
nese by  this  method,  the  true  result  is  50.5  per  cent. 

Pattinson's  Method.* 

Dissolve  in  hydrochloric  acid  such  a.  quantity  of  the  sample  as  shall 
contain  not  more  than  .25  gramme  of  manganese.  In  high  manganese 
ores  add  enough  ferric  chloride  to  the  solution  to  make  the  iron  and  man- 
ganese contents  about  equal.  Add  calcium  carbonate  to  the  solution  until 
it  is  slightly  red  in  color  and  acidulate  by  adding  hydrochloric  acid  until 
the  red  color  disappears.  Add  sufficient  zinc  chloride  in  solution  to  give 
.5  gramme  metallic  zinc.  Heat  to  boiling,  dilute  with  boiling  water  to 
300  c.c.,  and  add  60  c.c.  of  a  solution  of  calcium  hypochlorite  containing 
33  grammes  to  the  litre.  To  the  solution  of  hypochlorite,  just  before 
using,  add  enough  hydrochloric  acid  to  give  it  a  faint  greenish  tinge  after 
agitation. 


*  Society  of  Chemical  Industry,  vol.  x.  No.  4. 


DETERMINATION  OF  MANGANESE   DIOXIDE.  245 

Finally  add  3  grammes  of  calcium  carbonate  diffused  in  15  c.c.  of 
boiling  water,  and,  after  stirring  well,  2  c.c.  of  methyl  alcohol. 

Filter  on  a  large  filter  and  wash  with  water  at  65°  C.  until  a  strip 
of  iodized  starch  paper  gives  no  indication  of  chlorine. 

Measure  into  a  beaker  100  c.c.  of  a  carefully  standardized  strongly  acid 
solution  of  ferrous  sulphate,  containing  10  grammes  of  iron  to  the  litre, 
and  place  the  precipitate  and  filter  in  it.  When  the  precipitate  has 
dissolved  add  cold  water  and  determine  the  excess  of  ferrous  sulphate 
by  a  standard  solution  of  potassium  bichromate. 

When  the  ore  contains  much  organic  matter  it  should  be  filtered,  off 
before  attempting  to  oxidize  the  ferrous  salt,  as  it  is  quite  impossible  in 
some  cases  to  destroy  the  organic  matter,  and  resolution  of  the  evaporated 
mass  in  hydrochloric  acid  causes  a  reduction  of  some  of  the  ferric  salt. 
See  also  the  Bismuthate  method,  page  121. 


DETERMINATION   OF  MANGANESE  DIOXIDE. 

Many  mangani.ferous  iron  ores  contain  manganese  in  a  higher  state 
of  oxidation  than  the  protoxide,  and  the  determination  of  the  excess  of  • 
oxygen  is  often  necessary.  All  ores  of  this  character  when  treated  with 
hydrochloric  acid  evolve  chlorine  gas,  which  is  easily  recognized  by  its  yel- 
lowish green  color  and  peculiarly  irritating  odor.  The  reaction  by  which 
chlorine  is  liberated  is  MnO2  -f  4HC1  =  MnCl2  -f-  2H2O  -f  2C1,  or  each 
molecule  of  manganese  dioxide  =  87  corresponds  to  2  molecules  of 
chlorine  =  70.90.  This  reaction  is  the  basis  of  Bunsen's  method  for  the 
estimation  of  the  amount  of  manganese  dioxide  in  manganese  ores,  which 
consists  in  driving  the  liberated  chlorine  into  a  solution  of  potassium 
iodide,  and  determining  the  amount  of  iodine  set  free  by  starch  and  hypo- 
sulphite solution.  When  the  method  given  on  page  68  for  determining 
sulphur  in  steel  is  in  use,  the  solutions  employed  in  carrying  out  that 
method  (with  the  exception  of  the  iodine  in  potassium  iodide)  can  be  used 
in  this,  or  they  may  be  prepared  by  the  directions  there  given,  for  use  in 
this  method. 


246 


ANAL  YSIS   OF  IRON  ORES. 


Bunsen's  Method. 

Weigh  from  .5  gramme  to  I  gramme  of  the  finely  ground  ore  and  place 
it  in  the  flask  a,  Fig.  98,  pour  in  10  c.c.  strong  hydrochloric  acid,  connect 
the  bent  tube  b  quickly  by  means  of  a  piece  of  rubber  tubing,  and  heat  the 
flask  gently  at  first  and  finally  to  boiling  to  drive  all  the  chlorine  over  into 
the  tube  ct  which  contains  a  strong  solution  of  pure  potassium  iodide  free 
from  iodate.  This  tube  is  placed  in  ice-water.  When  all  the  chlorine 


FIG.  98. 


has  been  expelled  from  the  flask  a  and  absorbed  in  c,  detach  the  latter, 
wash  its  contents  into  a  large  dish,  add  a  little  starch  solution,  and  run  in 
the  hyposulphite  until  the  blue  color  just  vanishes.  If,  as  in  the  example 
given  on  page  71,  i  c.c.  of  the  hyposulphite  solution  is  equal  to  .01267 
gramme  of  iodine,  and  I  equivalent  of  chlorine  =  35-45  replaces  I  equiva- 
lent of  iodide  =  126.85  in  the  potassium  iodide,  I  c.c.  of  the  hyposulphite 


DETERMINATION  OF  MANGANESE   DIOXIDE.  247 

solution  would  be  equal  to  (126.85  :  3545  :  :  .01267  :  .003541)  .003541 
gramme  of  chlorine;  and,  as  I  equivalent  of  manganese  dioxide  =87  is 
equal  to  2  equivalents  of  chlorine  =  70.90,  I  c.c.  of  the  hyposulphite  would 
be  equal  to  (70.90  :  87  :  :  .003541  :  .004345)  .004345  gramme  manganese 
dioxide. 

Determination  by  Ferrous  Sulphate. 

In  most  laboratories,  however,  it  is  generally  more  convenient  to 
estimate  the  amount  of  manganese  dioxide  in  an  ore  by  determining  its 
oxidizing  power  on  a  solution  of  ferrous  salt.  The  reaction  is  2FeSO4 
+  MnO2  +  2H2SO,  =  Fe2(SO,)3  +  MnSO,  +  2H2O,  or  2  equivalents  of  iron 
=  112  are  equal  to  I  equivalent  of  manganese  dioxide  =  87.  Grind  in  an 
agate  or  Wedgwood  mortar  about  10  or  15  grammes  of  ferrous  sulphate  or 
ferrous-ammonium  sulphate,  and  weigh  out  two  portions,  one  of  2  grammes 
and  one  of  from  3  to  8  grammes,  according  to  the  quality  of  the  man- 
ganese ore.  One  gramme  of  pure  manganese  dioxide  would  oxidize  1.2874 
grammes  of  iron,  equal  to  nearly  6.5  grammes  of  ferrous  sulphate,  or  more 
than  9  grammes  of  ferrous-ammonium  sulphate.  Transfer  the  2-gramme 
portion  to  the  dish,  add  a  large  amount  of  water  and  about  5  c.c.  hydro- 
chloric acid,  and  pour  in  3  grammes  of  zinc  dissolved  in  10  c.c.  sulphuric 
acid  diluted  with  enough  water  to  dissolve  the  zinc  sulphate  completely. 
Titrate  with  the  standard  solution  of  potassium  permanganate  or  bichromate 
in  the  usual  way,  and  calculate  the  amount  of  iron  in  I  gramme  of  the 
ferrous  salt  used.  Weigh  I  gramme  of  the  finely  ground  ore,  transfer  to  the 
flask  A  (Fig.  96,  page  234),  and  add  to  it  the  larger  portion  of  the  ferrous  salt 
previously  weighed  out.  Connect  the  flask  as  shown,  and  pass  in  a  current 
of  carbonic  acid  until  the  air  has  been  driven  out.  Now  pour  into  the 
flask  A,  by  means  of  a  small  funnel  attached  to  B,  10  c.c.  hydrochloric 
acid  and  30  c.c.  water,  reconnect  the  carbonic  acid  apparatus,  and  while  the 
current  of  carbonic  acid  is  passing  dissolve  the  ore,  heating  the  flask,  and 
shaking  it  from  time  to  time  as  necessary.  When  the  ore  is  all  decom- 
posed, stop  the  current  of  carbonic  acid  for  a  moment,  remove  the  light, 
and  allow  the  water  in  E  to  flow  back  into  the  flask  A.  Transfer  the 
solution  to  the  dish,  add  3  grammes  zinc  dissolved  in  sulphuric  acid,  and 


248  ANAL  YSIS    OF  IRON  ORES. 

titrate  with  the  standard  solution.  From  the  titration  of  the  ferrous  salt 
calculate  the  amount  of  iron  in  the  amount  used  in  the  solution  of  the  ore, 
and  subtract  from  this  the  amount  found  by  this  last  titration ;  the  differ- 
ence is  the  weight  of  iron  oxidized  by  the  chlorine  liberated  from  the 
manganese  dioxide  in  the  ore.  Then,  as  112  parts  of  iron  correspond 
to  87  parts  of  manganese  dioxide,  multiply  the  above  weight  of  iron 
by  87  and  divide  by  112,  and  the  result  is  the  weight  of  manganese 
dioxide  in  the  ore. 

The  total  manganese  having  been  determined  by  one  of  the  methods 
previously  given,  subtract  from  it  the  amount  of  manganese  as  manga- 
nese dioxide  (found  by  multiplying  the  weight  ot  manganese  dioxide  by 
.63218),  and  calculate  the  difference  to  manganous  oxide  by  multiplying 
by  1.2909. 


DETERMINATION     OF    SILICA,     ALUMINA,     LIME,     MAG- 
NESIA,   MANGANESE    OXIDE,    AND    BARYTA. 

Treatment  of  iron  ores  with  hydrochloric  acid  leaves  a  residue  which 
only  in  very  rare  instances  consists  of  silica  alone,  being  usually  silicates 
of  aluminum,  calcium,  and  magnesium,  mixed  with  an  excess  of  silica. 
These  silicates  are  often  much  more  complicated,  and  contain,  besides  the 
substances  enumerated  above,  ferrous  oxide,  soda,  potash,  and  manganese 
oxide.  With  these  silicates  are  occasionally  found  titanic  acid,  titaniferous 
iron,  chrome  iron  ore,  barium  sulphate,  and  ferrous  sulphide,  besides  or- 
ganic matter,  and  sometimes  graphite.  As  this  residue  must  be  fused 
with  sodium  carbonate  in  order  to  decompose  it,  and  the  introduction 
of  sodium  salts  into  the  main  solution  is  not  desirable,  the  two  portions 
of  the  ore  (the  soluble  and  the  insoluble  in  hydrochloric  acid)  should  be 
analyzed  separately. 

Place  I  gramme  of  ore  in  a  No.  I  beaker,  add  15  c.c.  hydrochloric  acid, 
cover  with  a  watch-glass,  and  digest  at  a  gentle  heat  until  the  ore  appears 
to  be  quite  decomposed,  add  a  few  drops  of  nitric  acid,  heat  until  the  action 
has  ceased,  and  then  wash  off  the  cover  with  a  fine  jet  of  water  and  evap- 
orate to  dryness.  Redissolve  in  hydrochloric  acid,  and  evaporate  to  dry- 


DETERMINATION  OF  SILICA,  ALUMINA,  ETC.  249 

ness  a  second  time  to  render  all  the  silica  insoluble.  Redissolve  in  IO  c.c. 
hydrochloric  acid  and  30  c.c.  water,  filter,  transfer  all  the  residue  to  the 
filter  (a  small  ashless  filter)  with  a  fine  jet  of  cold  water,  using  a  "  police- 
man" to  detach  any  adhering  particles  from  the  beaker,  and  wash  the  filter 
with  a  little  hydrochloric  acid  and  plenty  of  cold  water.  Allow  the  filtrate 
and  washings  to  run  into  a  No.  5  beaker,  and  ignite  and  weigh  the  residue 
as  "  Insoluble  Silicious  Matter." 

Add  to  the  insoluble  matter  in  the  crucible  about  ten  times  its  weight 
of  pure  dry  sodium  carbonate  and  fuse  it.  Run  the  fusion  well  up  on  the 
sides  of  the  crucible,  cool,  and  dissolve  in  hot  water.  Transfer  to  a  plati- 
num dish,  dissolve  any  particles  adhering  to  the  crucible  in  hydrochloric 
acid,  and  add  this  to  the  solution  in  the  dish.  Acidulate  with  hydrochloric 
acid,  evaporate  to  dryness,  moisten  with  hydrochloric  acid  and  water,  evap- 
orate to  dryness  a  second  time  to  render  silica  insoluble,  then  pour  into  the 
dish  5  c.c.  hydrochloric  acid  and  15  c.c.  water,  and  stand  it  in  a  warm  place 
for  some  time.  Dilute  with  about  20  c.c.  water,  filter  on  a  small  ashless 
filter,  wash  well  with  hot  water,  receiving  the  filtrate  and  washings  in  a 
small  beaker,  dry,  ignite,  and  weigh.  Treat  the  ignited  precipitate  with 
hydrofluoric  acid  and  a  drop  or  two  of  sulphuric  acid,  evaporate  to  dryness, 
ignite,  and  weigh  again.  The  difference  between  the  two  weights  is  silica. 
If  the  difference  between  the  last  weight  and  the  weight  of  the  empty 
crucible  is  more  than  a  milligramme  or  two,  the  residue  must  be  examined 
and  its  nature  determined.  This  residue  may  consist  of  titanic  acid,  barium 
sulphate,  alumina,  or  sodium  sulphate  (from  imperfect  washing  of  the 
silica).  If  it  is  titanic  acid  or  alumina,  the  weight  must  be  added  to  the 
weights  of  the  alumina,  etc. 

Return  the  filtrate  from  the  silica  to  the  dish  in  which  it  was  previously 
contained,  heat  to  boiling,  add  a  few  drops  of  bromine-water  and  an  excess 
of  ammonia,  boil  until  it  smells  but  faintly  of  ammonia,  filter  on  a  small 
ashless  filter,  wash  well  with  hot  water,  dry,  ignite,  and  weigh  as  alumina, 
etc.  Besides  alumina  this  precipitate  may  contain  titanic  acid,  chromium 
sesquioxide,  ferric  oxide,  manganous  oxide,  and  phosphoric  acid. 

Return  the  filtrate  from  this  precipitate  to  the  dish,  evaporate  down 
to  about  100  c.c.,  add  ammonium  oxalate  and  ammonia,  boil  for  a  few 


250  A  ANALYSIS   OF  IRON  ORES. 

minutes,  allow  the  precipitate  to  settle,  filter  on  a  small  ashless  filter, 
ignite  finally  for  five  minutes  over  a  blast-lamp,  and  weigh  as  lime.  To 
the  filtrate  from  the  lime  add  microcosmic  salt  and  about  one-third  the 
volume  of  the  solution  of  ammonia,  cool  in  ice-water,  stir  vigorously 
several  times,  and  allow  to  stand  overnight  so  that  the  precipitated 
ammonium-magnesium  orthophosphate  may  settle  properly,  filter,  wash 
with  water  containing  one-third  its  volume  of  ammonia  and  about  100 
grammes  of  ammonium  nitrate  to  the  litre,  ignite  carefully,  and  weigh. 
Dissolve  the  precipitate  in  the  crucible  in  a  little  water  containing  from 
5  to  10  drops  hydrochloric  acid,  filter  through  a  small  ashless  filter, 
which  dry,  ignite,  and  weigh.  The  difference  between  the  two  weights 
is  magnesium  pyrophosphate,  which,  multiplied  by  .36212,  gives  the  weight 
of  magnesia. 

When  barium  has  been  shown  to  exist  in  the  ore,  as  noted  on 
page  248,  heat  the  filtrate  from  the  "  Insoluble  Silicious  Matter"  to  boiling, 
add  a  few  drops  of  sulphuric  acid,  boil  for  a  few  minutes  to  allow  the 
precipitate  to  settle,  filter  on  a  small  ashless  filter,  allowing  the  filtrate 
and  washings  to  run  into  a  No.  5  beaker,  dry,  ignite,  and  weigh  as  barium 
sulphate,  which,  multiplied  by  .65648,  gives  the  weight  of  barium  oxide. 

To  the  cold  filtrate  from  the  barium  sulphate  add  ammonia  until  the 
solution  is  nearly  neutralized,  then  add  a  solution  of  ammonium  carbonate 
until  a  slight  permanent  precipitate  is  formed  which  fails  to  dissolve  after 
vigorous  stirring,  and  redissolve  this  by  the  careful  addition  of  hydro- 
chloric acid,  drop  by  drop,  stirring  well,  and  allowing  the  solution  to  stand 
for  a  short  time  after  each  addition  of  hydrochloric  acid.  As  soon  as  the 
solution  clears,  add  a  solution  of  ammonium  acetate,  made  by  slightly 
acidulating  5  c.c.  of  ammonia  by  acetic  acid,  dilute  to  about  600  c.c.  with 
boiling  water,  and  boil  for  a  few  minutes.  Allow  the  precipitate  to  settle, 
decant  the  clear  liquid  through  a  large  washed  filter,  pour  the  precipitate 
on  the  filter,  and  wash  it  two  or  three  times  with  boiling  water.  With  the 
aid  of  a  platinum  spatula  return  the  precipitate  to  the  beaker  in  which  the 
precipitation  was  made,  dissolving  any  portion  remaining  on  the  filter  or 
adhering  to  the  spatula  in  dilute  hydrochloric  acid,  allowing  the  acid  to  run 
into  the  beaker  containing  the  precipitate.  Wash  the  filter  thoroughly  with 


DETERMINATION   OF  SILICA,  ALUMINA,  ETC.  2$  I 

cold  water,  and  evaporate  the  solution  and  washings  to  dryness.  Redis- 
solve  in  dilute  hydrochloric  acid,  filter  into  a  large  platinum  dish,  dilute 
with  hot  water,*  heat  to  boiling,  and  add  a  slight  excess  of  ammonia. 
Boil  for  a  few  minutes  to  make  the  precipitate  granular  and  expel  the 
excess  of  ammonia,  and  filter  on  an  ashless  filter  (using  the  filter-pump 
and  cone,  page  27,  with  very  slight  pressure,  if  practicable).  Dissolve  any 
particles  of  the  precipitate  adhering  to  the  dish  in  a  very  few  drops  of 
hydrochloric  acid,  heating  the  bottom  of  the  dish  slightly,  wash  off  the 
rod  and  cover,  and  wash  down  the  sides  of  the  dish  with  hot  water,  add 
a  slight  excess  of  ammonia,  heat  gently  until  the  precipitate  of  ferric 
hydrate  separates,  wash  this  onto  the  filter,  and  wash  the  precipitate  thor- 
oughly with  hot  water.  Dry  the  filter  and  precipitate  carefully,  transfer 
the  latter  to  a  weighed  crucible,  burn  the  filter  in  a  wire,  add  the  ash  to  the 
precipitate,  and  heat  the  crucible,  keeping  it  carefully  covered,  and  raising 
the  heat  very  gradually  to  expel  the  last  traces  of  moisture  from  the  pre- 
cipitate of  ferric  hydrate.  Finally  heat  the  crucible  to  bright  redness,  and 
then  to  the  highest  temperature  of  the  blast-lamp  for  from  five  to  ten 
minutes.  Cool,  ignite,  and  weigh  as  ferric  oxide  -f-  alumina  -f-  phosphoric 
acid  (-J-  titanic  acid  -f-  chromic  oxide  -f  arsenic  acid). 

Add  the  filtrate  and  washings  from  the  acetate  precipitation  to  those 
from  the  precipitation  by  ammonia,  evaporate  down  to  about  200  c.c.  in 
a  platinum  dish,  filter  off  any  slight  precipitate  of  ferric  oxide  (which  must 
be  ignited,  weighed,  and  the  weight  added  to  that  of  the  ferric  oxide,  etc.), 
add  from  20  to  30  drops  of  acetic  acid,  heat  to  boiling,  and  pass  a  current 
of  hydrogen  sulphide  through  the  solution  for  fifteen  or  twenty  minutes, 
keeping  the  solution  hot  during  the  passage  of  the  gas.  Filter  off  the 
precipitated  copper,  zinc,  nickel,  and  cobalt  sulphides,  wash  with  hydrogen 
sulphide  water  containing  a  little  free  acetic  acid,  and  to  the  filtrate  add 


*  The  distilled  water  used  in*  the  complete  analysis  of  iron  ores  should  never  be  heated  in  glass 
vessels  for  any  length  of  time,  as  glass  is  sensibly  attacked  by  it.  An  experiment  in  which  distilled 
water  free  from  residue  was  heated  for  twelve  hours  in  a  Bohemian  flask  showed  that  the  water  dis- 
solved 52  milligrammes  of  solid  matter  to  the  litre,  of  which  26  milligrammes  were  silica.  The 
water  should  always  be  heated  in  platinum  or  porcelain  dishes,  or  in  tin-lined  copper  flasks.  For 
convenience,  the  water  may  be  poured  into  the  washing-flasks  for  immediate  use. 


252  ANALYSIS   OF  IRON  ORES. 

excess  of  ammonia  and  ammonium  sulphide.  Allow  the  precipitated 
manganese  sulphide  to  settle,  decant  the  clear,  supernatant  liquid  through 
a  filter,  but  before  pouring  the  precipitate  on  the  filter  remove  the  beaker 
containing  the  filtrate  and  substitute  a  clean  beaker,  as  the  precipitate 
is  almost  certain  at  first  to  run  through  the  filter.  Wash  the  precipitate 
and  filter  with  water  containing  a  little  ammonium  sulphide,  add  the  clear 
filtrate  and  washings  together,  and  stand  them  aside.  Dissolve  the  pre- 
cipitate of  manganese  sulphide  on  the  filter  in  dilute  hydrochloric  acid, 
and  wash  the  filter  thoroughly  with  hot  water,  receiving  the  solution  and 
washings  in  a  small  beaker.  Heat  to  boiling  to  expel  hydrogen  sul- 
phide, and,  when  the  excess  is  driven  off,  destroy  the  last  traces  with  a 
little  bromine-water,  transfer  the  solution  to  a  platinum  dish,  and  precipi- 
tate by  microcosmic  salt  and  ammonia  as  directed  on  page  1 10.  Filter, 
wash,  ignite,  and  weigh  as  manganese  pyrophosphate,  which,  multiplied 
by  .50011,  gives  the  weight  of  manganous  oxide. 

Acidulate  the  filtrate  from  the  manganese  sulphide  with  hydrochloric 
acid,  boil  off  all  the  hydrogen  sulphide,  filter  from  the  sulphur  deposited 
by  this  operation  into  a  platinum  dish,  add  an  excess  of  ammonia  and 
ammonium  oxalate,  filter,  ignite,  and  heat  at  the  highest  temperature  of 
the  blast-lamp  for  fifteen  minutes,  cool,  and  weigh  as  lime. 

Precipitate  the  magnesia  in  the  filtrate  as  directed  on  page  250,  and 
determine  the  weight  of  magnesium  pyrophosphate,  which,  multiplied  by 
.36212,  gives  the  weight  of  magnesia. 

By  adding  the  elements  determined  in  the  insoluble  portion  to  the 
similar  ones  in  the  soluble  portion,  we  get  the  total  amounts  of  each  in 
the  ore.  Thus,  we  have  from  the  above  analysis  silica,  ferric  oxide  -f 
alumina  -|-  phosphoric  acid  -f-  chromic  oxide  -f-  titanic  acid  -f  arsenic  acid, 
manganese  oxide,  lime,  and  magnesia,  and  it  becomes,  of  course,  neces- 
sary to  calculate  properly  the  iron  in  its  different  states  of  oxidation  and 
to  determine  the  amount  of  alumina  in  the  ore.  It  is  much  more  accu- 
rate to  determine  in  separate  portions  of  the  ore  the  amounts  of  phos- 
phoric acid,  arsenic  acid,  chromic  oxide,  ferric  oxide,  and  titanic  acid  than 
to  attempt  to  make  the  separation  in  the  precipitate  obtained  in  this  por- 
tion. Therefore,  knowing  the  amounts  of  these  substances,  the  ferric 


DETERMINATION  OF  SILICA,  ALUMINA,  ETC.  253 

oxide  from  the  volumetric  determination  of  iron,  as  previously  described, 
and  the  amount  of  each  of  the  others  as  found  by  one  of  the  methods 
given,  add  together  the  weights  of  the  ferric  oxide,  the  phosphoric  acid, 
the  chromic  oxide,  the  titanic  acid,  and  the  arsenic  acid  in  one  gramme 
of  the  ore,  and  subtract  the  sum  from  the  weight  of  the  precipitate  ob- 
tained in  the  above  analysis,  the  result  is  the  weight  of  alumina  in  one 
gramme  of  the  ore. 

Iron  may  exist  in  an  ore  in  several  conditions,  as  Fe2O3,  as  FeO,  as 
FeS2,  as  FeAs2,  etc.  While  it  may  not  always  be  possible  to  determine 
the  exact  conditions  in  which  it  exists,  the  rule  usually  followed  is,  after 
subtracting  from  the  sulphur  existing  as  sulphides  (page  237)  the  amount 
necessary  to  form  copper  sulphide,  nickel  sulphide,  etc.,  to  calculate  the 
remainder  as  FeS2  by  multiplying  the  weight  of  sulphur  by  1.87336.  The 
weight  of  sulphur  subtracted  from  this  gives  the  weight  of  iron  in  the 
FeS2.  Now  from  the  weight  of  FeAs2  subtract  the  weight  of  arsenic,  and 
the  result  is  the  weight  of  iron  existing  as  iron  in  the  FeAs2.*  Add  the 
iron  in  the  FeS2  to  the  iron  in  the  FeAs2,  and  subtract  this  weight  from  the 
iron  found  as  ferrous  oxide,  the  remainder  calculated  to  ferrous  oxide  is 
the  amount  of  ferrous  oxide  in  the  ore.  Subtract  the  total  amount  of 
iron  found  originally  by  titration  to  exist  as  ferrous  oxide  from  the  total 
iron  found  in  the  ore,  and  calculate  the  remainder  to  ferric  oxide. 

When  an  iron  ore  contains  only  a  very  small  amount  of  manganese, 
the  acetate  separation  may  be  omitted  in  the  method  as  given  above, 
which  simplifies  and  shortens  the  operation  very  materially.  In  this 
event  transfer  the  filtrate  from  the  insoluble  silicious  matter  at  once  to  a 
large  platinum  dish,  heat  to  boiling,  add  a  few  c.c.  of  bromine-water  and 
then  excess  of  ammonia,  boil,  filter  the  ferric  oxide,  etc.,  on  an  ashless 
filter,  dry,  ignite,  and  weigh,  as  described  above.  The  manganese  will 
be  in  the  precipitate  after  ignition  as  manganoso-manganic  oxide,  and 
the  amount  calculated  from  the  determination  of  manganese  made  in  a 
separate  portion  of  the  ore  must  be  subtracted  from  the  weight  of  the 
above  precipitate  in  calculating  the  amount  of  alumina. 


*  All  the  weights,  of  course,  are  calculated  to  one  gramme  of  ore. 


254  ANALYSIS   OF  IRON  ORES. 

The  lime  and  magnesia  are  determined  in  the  filtrate  from  the  ferric 
oxide,  etc.,  provided,  of  course,  that  the  ore  contains  only  minute  amounts 
of  nickel,  copper,  etc. 

The  same  general  method  described  above  is  applicable  when  the 
ore  contains  quite  a  large  amount  of  titanic  acid,  so  much,  in  fact,  as  to 
cause  the  cloudiness  in  the  filtrate  from  the  insoluble  silicious  matter, 
as  noted  on  page  240.  Whenever  an  acetate  separation  is  necessary  in 
an  ore  of  this  character,  the  precipitate  must  be  filtered  on  an  ashless 
filter,  and  this,  as  well  as  the  filter  containing  any  insoluble  matter  from 
the  resolution  of  the  acetate  precipitate,  must  be  ignited  and  examined 
for  titanic  acid  by  treating  the  residue  with  hydrofluoric  and  sulphuric 
acids,  heating  to  redness,  fusing  with  sodium  carbonate,  dissolving  in 
hydrochloric  acid  and  water,  and  precipitating  by  ammonia.  The  pre- 
cipitate so  obtained  is  to  be  filtered,  ignited,  and  the  weight  added  to  that 
of  the  ferric  oxide,  etc.  Ilmenite  even,  when  very  finely  ground  in  an 
agate  mortar,  is  frequently  capable  of  being  almost  entirely  decomposed 
by  hydrochloric  acid,  and  when  this  is  the  case  it  is  of  advantage  to  use 
this  method  of  analysis.  It  may  be  necessary,  however,  under  certain 
circumstances  to  decompose  the  ore  at  the  start  by  fusing  with  potassium 
bisulphate.  To  carry  out  this  method,  place  I  gramme  of  the  ore,  which 
has  been  ground  as  fine  as  possible  in  an  agate  mortar,  in  a  large  plati- 
num crucible,  add  10  grammes  of  pure  potassium  bisulphate,*  and  heat 
the  crucible,  carefully  covered,  over  a  very  low  light  until  the  bisulphate  is 
melted.  It  is  necessary  to  watch  this  operation  most  carefully,  for  the 
bisulphate  has  a  strong  tendency  to  boil  over,  and  only  unremitting  atten- 
tion on  the  part  of  the  analyst  will  prevent  the  loss  of  the  analysis.  It 
is  well  at  the  start  to  stand  by  the  crucible  and  raise  the  lid  slightly  at 
very  short  intervals  to  watch  the  condition  and  progress  of  the  fusion. 
The  lid  should  be  held  just  over  the  crucible  and  in  a  horizontal  position, 
otherwise  the  particles  which  have  spirted  on  it  from  the  mass  in  the  cruci- 
ble may  run  to  the  edge  of  the  lid  and,  when  the  latter  is  replaced,  down 
the  outside  of  the  crucible.  Raise  the  heat  very  gradually,  keeping  the 

*  See  page  49. 


DETERMINATION  OF  SILICA,  ALUMINA,  ETC.  2$$ 

mass  just  liquid  and  the  temperature  at  the  point  at  which  slight  fumes 
of  sulphuric  anhydride  are  given  off  when  the  lid  is  raised,  until  the 
bottom  of  the  crucible  is  dull  red.  When  the  ore  is  completely  decom- 
posed, remove  the  light,  take  off  the  lid  of  the  crucible,  and  incline  the 
latter  at  such  an  angle  that  the  fused  mass  may  run  together  on  one  side 
of  the  crucible  and  as  near  the  top  as  possible.  Allow  it  to  cool  in  this 
position ;  when  cold  it  is  easily  detached  from  the  crucible.  Place  the 
crucible  and  lid  in  a  No.  4  beaker  half  full  of  cold  water,  and  the  fused 
mass  in  a  little  basket  made  of  platinum  gauze.  Pour  into  the 
beaker  enough  strong  aqueous  solution  of  sulphurous  acid  to  raise  the 
liquid  to  the  top  of  the  basket,  and  allow  the  fusion  to  dissolve,  which 
may  require  twelve  hours.  Wash  with  a  jet  of  cold  water,  and  remove  the 
basket,  the  crucible,  and  the  lid,  stir  the  liquid,  which  should  smell  strongly 
of  sulphurous  acid,  and  allow  the  insoluble  matter  to  settle.  Filter  on  an 
ashless  filter,  wash  well  with  cold  water,  dry,  ignite,  and  weigh.  Treat 
with  hydrofluoric  acid  and  2  or  3  drops  of  sulphuric  acid,  evaporate  to 
dryness,  ignite,  and  weigh.  The  difference  between  the  weights  is  silica. 
If  any  appreciable  residue  remains  in  the  crucible,  fuse  with  a  little  sodium 
carbonate,  treat  with  sulphuric  acid,  and  add  to  the  main  filtrate.  To  the 
main  filtrate,  which  should  be  quite  colorless  and  smell  strongly  of  sul- 
phurous acid,  add  a  clear  filtered  solution  of  20  grammes  of  sodium  acetate 
and  one-sixth  of  its  volume  of  acetic  acid  (1.04  sp.  gr.),  heat  to  boiling,  and 
boil  for  a  few  minutes.  Allow  the  precipitate  to  settle,  filter  on  an  ashless 
filter,  wash  thoroughly  with  hot  water  containing  one-sixth  its  volume  of 
acetic  acid,  and  finally  with  hot  water,  dry,  ignite,  and  weigh  as  titanic  acid. 
This  precipitate,  however,  may  not  be  quite  pure,  as  small  amounts  of 
ferric  oxide  and  alumina  may  be  carried  down  with  it.  The  best  plan  to 
pursue  is  to  fuse  with  sodium  carbonate,  dissolve  in  water,  filter,  wash, 
dry,  and  fuse  the  insoluble  sodium  titanate,  etc.,  with  sodium  carbonate, 
treat  the  cooled  mass  in  the  crucible  with  sulphuric  acid,  and  precipitate 
and  determine  the  titanic  acid  as  directed  above.  The  two  filtrates  from 
the  treatment  of  the  first  precipitate  of  titanic  acid  may  contain  a  little 
ferric  oxide  and  alumina.  To  recover  this,  boil  down  the  last  filtrate 
until  the  greater  part  of  the  sulphurous  acid  has  been  driven  off,  add 


256  ANALYSIS   OF  IRON  ORES. 

bromine-water  to  oxidize  the  iron,  acidulate  the  aqueous  filtrate  from  the 
sodium  carbonate  fusion  with  sulphuric  acid,  add  it  to  this  solution,  boil 
the  united  solutions  down  in  a  platinum  dish  to  a  convenient  volume,  and 
add  a  slight  excess  of  ammonia.  Boil  the  solution  until  it  smells  faintly 
but  decidedly  of  ammonia,  filter,  and  wash  slightly.  Redissolve  the  precipi- 
tate in  hydrochloric  acid,  and  reprecipitate  by  ammonia,  filter,  wash,  ignite, 
and  weigh  as  ferric  oxide  and  alumina  to  be  added  to  the  main  precipitate. 
Boil  the  main  filtrate  and  washings  down  in  a  large  platinum  dish  after 
adding  enough  bromine-water  to  oxidize  all  the  iron,  add  hydrochloric  acid 
from  time  to  time  when  necessary  to  keep  the  iron  in  solution,  and,  when 
reduced  to  a  convenient  bulk,  nearly  neutralize  by  ammonia,  and  boil. 
Filter,  and  wash  the  precipitate  two  or  three  times,  redissolve  and  re- 
precipitate  by  ammonia,  filter,  wash,  dry,  ignite,  and  weigh  as  ferric  oxide 
-(-  alumina  -j-  phosphoric  acid.  Fuse  this  precipitate  fora  long  time  and 
at  a  high  temperature  with  sodium  carbonate,  dissolve  in  water,  wash  by 
decantation,  redissolve  the  residue  of  ferric  oxide,  etc.,  in  hydrochloric  acid, 
and  determine  the  iron  by  titration.  The  alumina  is  obtained  by  differ- 
ence, the  phosphoric  acid  being  determined  in  a  separate  portion.  In  the 
filtrate  from  the  ferric  oxide  +  alumina  -f  phosphoric  acid  determine  man- 
ganese, lime,  and  magnesia  in  the  usual  way. 


DETERMINATION    OF    SILICA. 

When  silica  alone  is  wanted  in  an  ore  a  more  rapid  method  is  some- 
times desirable.  In  this  case  dissolve  I  gramme  of  the  ore  in  hydrochloric 
acid,  evaporate  to  dryness,  redissolve  in  dilute  hydrochloric  acid,  filter  on  an 
ashless  filter,  wash,  dry,  ignite,  and  weigh  the  insoluble  silicious  matter. 
Treat  this  in  the  crucible  with  hydrofluoric  acid  and  a  few  drops  of  sul- 
phuric acid,  evaporate  to  dryness,  ignite,  and  weigh.  It  is  evident  now  that 
if  the  insoluble  silicious  matter  contains  calcium,  magnesium,  potassium,  or 
sodium,  the  loss  of  weight,  which  in  the  absence  of  these  elements  would 
represent  the  silica  volatilized  as  silicon  tetrafluoride,  will  be  decreased  by 
the  amount  of  sulphuric  acid  which,  uniting  with  these  elements,  remains 


SEPARATION  OF  ALUMINA   FROM  FERRIC   OXIDE.  257 

as  a  part  of  the  residue  in  the  crucible.  It  is  a  simple  operation,  however, 
to  fuse  this  residue  with  sodium  carbonate,  dissolve  in  water,  acidulate  with 
hydrochloric  acid,  heat  to  boiling,  add  solution  of  barium  chloride  and  filter 
off,  and  weigh  the  precipitated  barium  sulphate.  This  being  accomplished, 
calculate  the  amount  of  sulphuric  anhydride,  and  add  its  weight  to  the  loss 
by  volatilization.  The  result  is  the  weight  of  silica.  When  the  ore 
contains  appreciable  amounts  of  barium  sulphate  this  method  is  not 
admissible. 

Separation  of  Alumina  from  Ferric  Oxide. 

Besides  the  indirect  method  for  determining  alumina,  it  is  sometimes 
necessary  or  convenient  to  make  a  direct  separation.  The  method  usually 
taken,  the  iron  and  alumina  being  in  solution  in  hydrochloric  acid,  is  as 
follows.  Add  to  the  solution  about  five  times  the  weight  of  the  oxides,  of 
citric  acid  (tartaric  acid  may  be  used,  but,  as  it  is  liable  to  contain  alumina, 
citric  acid  is  preferable)  and  excess  of  ammonia.  If  the  solution  remains 
clear,  heat  to  boiling,  and  add  a  fresh  solution  of  ammonium  sulphide  until 
all  the  iron  is  precipitated.  If  the  solution  does  not  remain  clear  on  the 
addition  of  ammonia,  acidulate  with  hydrochloric  acid,  add  more  citric  acid, 
and  then  excess  of  ammonia.  Allow  the  ferrous  sulphide  to  settle,  decant 
the  clear  liquid  through  a  washed  filter,  throw  the  precipitate  on  the  filter, 
and  wash  it  well  with  water  containing  ammonium  sulphide  and  ammonium 
chloride,  changing  the  beaker  into  which  the  washings  run  before  each 
addition  of  wash-water,  and  keeping  the  funnel  well  covered  with  a  watch- 
glass.  Unite  the  filtrate  and  washings,  acidulate  with  hydrochloric  acid, 
boil  until  the  precipitated  sulphur  agglomerates,  filter  into  a  platinum  dish, 
and  evaporate  to  dryness.  Heat  carefully  until  the  ammonium  chloride  is 
volatilized  and  there  remains  in  the  dish  a  mass  of  carbonaceous  matter 
from  the  decomposition  of  the  citric  acid.  The  expulsion  of  the  last  traces 
of  water  from  the  ammonium  chloride  nearly  always  causes  loss  by  spirt- 
ing, but  the  difficulty  may  be  entirely  avoided  by  placing  the  dish  in  one 
of  the  holes  of  the  air-bath  overnight,  after  having  lightly  coated  the  upper 
edge  of  the  dish  with  paraffine  or  grease  to  prevent  the  ammonium  chloride 
from  creeping  over  the  top.  This  long  heating  expels  the  last  traces  of 
water  without  the  least  disturbance,  and  the  dish  may  at  once  be  placed 


258  ANALYSIS   OF  IRON  ORES. 

over  a  Bunsen  burner,  and  the  mass  in  it  decomposed  without  fear  of  loss. 
Transfer  the  carbonaceous  matter  to  a  crucible,  wiping  out  the  dish  care- 
fully with  filter-paper,  and  placing  these  in  the  crucible  also.  Burn  off  the 
carbon  in  the  crucible,  fuse  the  residue  with  sodium  carbonate  and  a  little 
sodium  nitrate,  treat  with  water,  transfer  to  a  platinum  dish,  dissolve  any 
adhering  particles  in  the  crucible  in  hydrochloric  acid,  add  this  to  the  solu- 
tion in  the  dish,  with  enough  hydrochloric  acid  to  acidulate  it,  heat  to  boil- 
ing after  diluting,  add  a  slight  excess  of  ammonia,  boil  until  the  solution 
smells  but  faintly  of  ammonia,  filter,  wash  thoroughly,  ignite,  and  weigh  as 
alumina.  This  precipitate  will  contain  any  phosphoric  and  titanic  acids 
that  may  have  been  in  the  original  solution.  They  may  be  separated  by 
the  methods  given  previously.  It  is  liable  to  contain  also  a  little  iron, 
which  is  almost  invariably  held  in  solution  by  the  ammonium  sul- 
phide. 

Dissolve  the  precipitate  of  ferrous  sulphide  on  the  filter  in  dilute  hot 
hydrochloric  acid,  allow  the  solution  and  washings  to  run  into  the  beaker 
in  which  the  precipitation  was  made,  add  a  little  nitric  acid,  evaporate  to 
dryness,  redissolve  in  as  little  dilute  hydrochloric  acid  as  possible,  filter  into 
a  platinum  dish,  dilute,  precipitate  by  ammonia,  filter,  wash,  dry,  ignite,  and 
weigh  as  ferric  oxide. 

Rose  *  suggested  the  method  based  on  the  solubility  of  alumina  in 
caustic  potash  or  soda.  When  the  iron  and  alumina  are  in  solution, 
evaporate  in  a  platinum  dish  until  syrupy,  add  a  strong  solution  of 
caustic  soda  or  potash  until  the  solution  is  strongly  alkaline,  and  then 
add  a  large  excess  of  the  precipitant,  and  boil  for  ten  or  fifteen  minutes ; 
or,  pour  the  nearly  neutral  solution  of  the  chlorides  into  a  boiling  solu- 
tion of  caustic  soda  or  potash  in  a  platinum  or  silver  dish,  in  a  thin 
stream,  stirring  continually.  Filter,  wash  with  hot  water,  carefully  acidu- 
late the  filtrate  with  hydrochloric  acid,  and  precipitate  the  alumina  by 
ammonia,  filter,  wash,  dissolve  in  hydrochloric  acid,  evaporate  to  dryness 
to  get  rid  of  silica,  redissolve,  filter,  and  determine  as  usual.  As  the 
ferric  oxide  precipitated  by  caustic  soda  or  potash  always  contains  alkali, 

*  Chimie  Anal.  Quant.  (French  ed.),  page  148. 


SEPARATION  OF  ALUMINA    FROM  FERRIC    OXIDE.  2 59 

it  must  be  dissolved  in  hydrochloric  acid,  precipitated  by  ammonia, 
filtered,  and  weighed  in  the  usual  manner. 

Rose  also  suggested  fusing  the  finely  ground  ignited  oxides  in  a 
silver  crucible  with  potassium  or  sodium  hydrate;  but  this  method,  as 
well  as  the  other,  is  open  to  the  objection  that  it  is  almost  impossible 
to  get  caustic  soda  or  potash  that  does  not  contain  alumina,  and  gener- 
ally there  is  more  in  the  reagent  than  in  the  ore. 

Rivot  suggested  the  following  method.  After  weighing  the  ignited 
iron  and  aluminum  oxides,  grind  them  very  fine,  weigh  them,  and  place 
in  a  porcelain  or  platinum  boat.  Place  the  boat  in  a  porcelain  or 
platinum  tube,  and  heat  to  redness  in  a  current  of  hydrogen  gas  until 
no  more  water  appears  to  come  off.  Replace  the  hydrogen  by  a  stream 
of  hydrochloric  acid  gas,  reheat  the  tube,  and  continue  the  current  as 
long  as  ferric  chloride  is  given  off.  Remove  the  boat,  and,  if  the  resi- 
due is  not  white,  repeat  the  operation.  Weigh  the  remaining  alumina, 
and  calculate  from  the  amount  of  the  oxides  used  the  total  amount  in 
the  ore. 

Rose  modified  this  method  by  substituting  a  crucible  and  tube  for  the 
boat,  etc.  The  apparatus  as  he  used  it  is  the  same  as  that  described 
for  the  determination  of  manganese  as  sulphide  (page  112). 

Wohler  suggested  the  method  of  separating  iron  and  alumina  by 
boiling  the  nearly  neutral  solution  with  an  excess  of  sodium  hyposul- 
phite. The  following  modification  of  this  method  *  appears  to  give  ex-* 
cellent  results,  and  has  the  advantage  of  doing  away  with  a  subsequent 
separation  of  phosphoric  acid  in  those  cases  in  which  it  has  not  been 
determined  in  another  portion.  The  ferric  oxide  and  alumina  from  I 
gramme  of  ore  being  in  solution  in  hydrochloric  acid,  dilute  to  400  or 
500  c.c.  with  cold  water,  and  add  ammonia  until  the  solution  becomes 
dark  red  in  color,  but  contains  no  precipitate.  Now  add  3.3  c.c.  hydro- 
chloric acid  (1.2  sp.  gr.)  and  2  grammes  sodium  phosphate,  dissolved  in 
water  and  filtered;  stir  until  the  precipitate  formed  is  dissolved  and  the 
solution  becomes  perfectly  clear  again.  Add  now  10  grammes  of  sodium 

*  Communicated  to  the  author  by  Mr.  S.  Peters  in  1879. 


260  ANALYSIS   OF  IRON  ORES. 

hyposulphite,  dissolved  in  water  and  filtered  if  necessary,  and  15  c.c.  of 
acetic  acid  (1.04  sp.  gr.),  heat  to  boiling,  boil  fifteen  minutes,  filter  as 
rapidly  as  possible  on  an  ashless  filter,  wash  thoroughly  with  hot  water, 
dry,  ignite  in  a  porcelain  crucible,  and  weigh  as  aluminum  phosphate, 
which,  multiplied  by  .41847,  gives  the  weight  of  alumina.  It  is  neces- 
sary in  burning  off  the  precipitate  to  raise  the  heat  very  carefully  until 
all  the  carbon  has  been  burned  off,  as  the  aluminum  phosphate  may 
fuse  and  make  it  almost  impossible  to  burn  off  the  carbon. 


DETERMINATION     OF    NICKEL,    COBALT,    ZINC,    AND 

MANGANESE. 

For  the  determination  of  these  elements  use  3  grammes  of  ore,  dis- 
solve in  hydrochloric  acid,  add  a  little  nitric  acid  or  potassium  chlorate 
to  oxidize  any  ferrous  oxide  in  the  ore,  evaporate  to  dryness,  redissolve 
in  hydrochloric  acid,  and  evaporate  a  second  time  if  necessary  to  get 
rid  of  all  nitric  acid.  As  noted  on  page  245,  when  the  ore  contains 
much  organic  matter,  dissolve  in  hydrochloric  acid  (if  there  is  much 
gelatinous  silica,  evaporate  to  dryness  or  the  filtration  will  be  much  re- 
tarded), filter,  add  nitric  acid  or  potassium  chlorate,  evaporate  to  dryness, 
redissolve  in  hydrochloric  acid,  and  evaporate  a  second  time  if  necessary, 
redissolve  in  10  c.c.  hydrochloric  acid  and  20  c.c.  water,  dilute,  filter  into 
a  No.  6  beaker,  and  proceed  exactly  as  directed  for  the  determination 
of  manganese  in  iron  and  steel  (page  108  et  seg.)  until  the  precipitate  by 
hydrogen  sulphide  is  obtained  and  filtered  off.  Determine  the  manga- 
nese, if  desired,  in  the  filtrate,  as  directed  on  page  1 10,  and  calculate  to 
manganous  oxide. 

Dry  and  ignite  the  precipitated  sulphides  of  nickel,  cobalt,  zinc,  cop- 
per, lead,  etc.,  in  a  porcelain  crucible,  transfer  to  a  small  beaker,  and 
dissolve  in  hydrochloric  acid,  with  the  addition  of  a  drop  or  two  of 
nitric  acid.  Evaporate  to  dryness,  redissolve  in  from  10  to  20  drops  of 
hydrochloric  acid,  dilute  to  50  or  60  c.c.,  heat  to  boiling,  and  pass  a 
current  of  hydrogen  sulphide  through  the  boiling  solution.  Filter  off 


DETERMINATION  OF  COPPER,    LEAD,   ARSENIC,    ETC.  26 1 

the  precipitated  sulphides  of  copper,  lead,  etc.,  and  wash  with  water 
containing  hydrogen  sulphide.  Evaporate  the  filtrate,  which  contains 
only  nickel,  cobalt,  and  zinc,  to  dryness.  To  the  dry  salts  in  the  bottom 
of  the  beaker  add  2  drops  of  strong  hydrochloric  acid,  dilute  to  150  c.c. 
with  cold  water,  and  pass  hydrogen  sulphide  through  the  solution  until 
it  is  thoroughly  saturated  with  the  gas.  If  a  white  precipitate  forms,  it 
is  zinc  sulphide.  Allow  to  stand  several  hours,  filter,  wash  with  hydro- 
gen sulphide  water  (the  zinc  sulphide  has  a  tendency  to  pass  through 
the  filter,  and  consequently  the  beaker  into  which  the  filtrate  is  received 
must  be  changed  before  the  precipitate  is  poured  on  the  filter),  dry,  and 
ignite  the  precipitate.  Heat  it  several  times  with  ammonium  carbonate 
to  drive  off  any  sulphuric  acid  that  may  have  been  formed  by  the  igni- 
tion, cool,  and  weigh  as  zinc  oxide.  The  precipitate  is  yellowish  white 
while  hot  and  greenish  white  when  cold.  If  it  should  carry  down  a 
little  cobalt  from  the  solution,  the  ignited  precipitate  of  zinc  oxide  is 
green  when  cold.  Pass  hydrogen  sulphide  through  the  filtrate  from  the 
zinc  sulphide  again,  and,  if  no  further  precipitate  appears,  add  a  few- 
drops  of  a  solution  of  .5  gramme  of  sodium  acetate  in  10  c.c.  water. 
If  this  occasions  a  white  precipitate,  filter  it  off,  after  standing,  as  in  the 
first  instance;  but  if  the  precipitate  is  black  (as  it  is  almost  certain  to  be 
if  the  instructions  given  above  are  strictly  followed),  add  the  rest  of  the 
sodium  acetate  solution,  heat  the  solution  to  boiling,  while  the  passage 
of  the  hydrogen  sulphide  is  continued,  allow  the  precipitate  to  settle, 
filter,  ignite,  and  treat  it  as  directed  for  the  separation  and  determina- 
tion of  nickel  and  cobalt  (page  1 88  et 


DETERMINATION  OF  COPPER,  LEAD,  ARSENIC,  AND 

ANTIMONY. 

Treat  10  grammes  of  the  finely  ground  ore  with  50  c.c.  hydrochloric 
acid,  add  a  little  potassium  chlorate  from  time  to  time,  and  increase  the 
heat  gradually  until  the  ore  is  perfectly  decomposed.  Dilute,  filter  into 
a  No.  5  beaker,  deoxidize  with  ammonium  bisulphite,  as  directed  on 


262  ANALYSIS   OF  IRON  ORES. 

page  81,  drive  off  the  excess  of  sulphurous  acid,  and  pass  hydrogen 
sulphide  through  the  solution  for  fifteen  or  twenty  minutes.  Allow  the 
solution  to  stand  for  some  hours  until  the  precipitate  has  settled  com- 
pletely and  the  solution  smells  but  faintly  of  hydrogen  sulphide.  Filter 
on  a  thin  felt  on  the  Gooch  crucible  or  small  cone,  wash  with  cold 
water,  and  suck  dry.  Transfer  the  felt  and  precipitate  to  a  small  beaker, 
using  a  little  asbestos  wad  in  the  forceps  to  wipe  off  any  adhering  precipi- 
tate from  the  large  beaker  and  the  crucible  or  cone,  and  digest  it  with 
a  few  c.c.  of  a  colorless  solution  of  potassium  sulphide.  Dilute  to  about 
100  c.c,  filter  on  another  felt,  and  wash  with  water  containing  a  little 
potassium  sulphide.  The  solution  contains  the  arsenic  and  antimony  sul- 
phides dissolved  in  potassium  sulphide,  while  the  copper  and  lead  sul- 
phides remain  on  the  felt.  Return  the  felt  with  the  precipitate  to  the 
beaker  from  which  they  were  filtered,  and  digest  with  hydrochloric  acid, 
with  the  addition  of  nitric  acid,  until  all  the  black  sulphides  are  dis- 
solved, dilute  with  a  little  hot  water,  and  filter.  Evaporate  the  filtrate, 
after  adding  a  few  drops  of  sulphuric  acid,  until  fumes  of  sulphuric 
anhydride  are  evolved,  allow  to  cool,  dilute  with  25  c.c.  cold  water,  add 
one-half  its  bulk  of  alcohol,  allow  to  settle,  filter  the  precipitated  lead 
sulphate  on  the  Gooch  crucible,  wash  with  alcohol  and  water,  heat  care- 
fully over  a  low  light,  and  weigh.  Treat  the  precipitate  on  the  felt  under 
a  slight  pressure  with  a  strongly  ammoniacal  solution  of  ammonium 
citrate,  to  dissolve  the  lead  sulphate,  wash  with  hot  water,  and  weigh. 
The  difference  between  the  two  weights  is  lead  sulphate,  which,  multiplied 
by  .68298,  gives  the  weight  of  lead,  or,  multiplied  by  .78879,  gives  the 
weight  of  lead  sulphide. 

Evaporate  the  filtrate  from  the  lead  sulphate  until  the  alcohol  is 
driven  off  and  the  solution  reduced  to  a  convenient  bulk,  transfer  to  a 
platinum  crucible,  and  precipitate  the  copper  on  the  small  platinum  cyl- 
inder by  the  battery  (Fig.  91).  The  weight  of  copper,  multiplied  by  1.25284, 
gives  the  weight  of  cuprous  sulphide. 

Acidulate  the  filtrate  of  potassium  sulphide  containing  arsenic  and 
antimony  in  solution  with  hydrochloric  acid,  and  allow  to  stand  in  a 
warm  place  until  all  the  hydrogen  sulphide  has  been  driven  off  and  the 


DETERMINATION  OF  COPPER,  LEAD,  ARSENIC,  ETC.  263 

arsenic  and  antimony  sulphides  mixed  with  the  excess  of  sulphur  have 
settled  completely.  Filter  on  a  thin  felt,  wash,  with  warm  water,  then  with 
alcohol,  and  finally  with  carbon  disulphide,  to  dissolve  the  excess  of  sul- 
phur. Transfer  the  felt  and  precipitate  to  a  small  beaker,  add  5  c.c. 
hydrochloric  acid  and  a  few  crystals  of  potassium  chlorate.  Digest  at  a 
low  temperature  for  some  time,  adding  occasionally  a  small  crystal  of 
potassium  chlorate,  finally  heat  a  little,  but  not  to  a  sufficiently  high  degree 
to  fuse  any  little  particles  of  separated  sulphur,  keeping  the  liquid  always 
full  of  the  products  of  decomposition  of  the  potassium  chlorate.  When 
all  the  arsenic  and  antimony  sulphides  are  dissolved,  dilute  with  about 
20  c.c.  of  warm  water,  and  add  a  few  small  crystals  of  tartaric  acid  to 
keep  the  antimony  in  solution.  Filter  from  the  asbestos,  using  as  little 
wash-water  as  possible  in  order  to  keep  down  the  volume  of  the  solution, 
add  a  slight  excess  of  ammonia  to  the  filtrate,  and  if  it  remains  clear 
5  c.c.  of  magnesia-mixture  and  one-third  the  volume  of  the  solution  of 
ammonia.  Cool  in  ice-water,  and  stir  vigorously  from  time  to  time  to 
precipitate  the  ammonium-magnesium  arsenate. 

Allow  to  stand  overnight,  filter,  and  determine  the  arsenic  as  directed 
on  page  200.  If  the  acid  solution  above  mentioned  becomes  cloudy 
upon  the  addition  of  ammonia,  acidulate  carefully  with  hydrochloric  acid, 
and  add  a  little  more  tartaric  acid.  Then  proceed  as  above  directed. 
The  weight  of  arsenic  calculated  from  the  amount  of  magnesium  pyro- 
arsenate,  multiplied  by  1.373,  gives  the  weight  of  ferrous  arsenide. 

Acidulate  the  filtrate  from  the  ammonium-magnesium  arsenate,  which 
contains  none  of  the  washings,  with  hydrochloric  acid,  so  that  the  solu- 
tion is  just  acid  to  test-paper,  dilute  with  hot  water  to  about  250  c.c., 
and  pass  hydrogen  sulphide  into  the  solution,  heating  it  gradually  to 
boiling.  Drive  ofT  the  excess  of  hydrogen  sulphide  with  a  current  of 
carbonic  acid,  filter  on  a  felt  in  the  Gooch  crucible,  wash  with  water, 
alcohol,  and  finally  with  carbon  disulphide  to  dissolve  any  free  sulphur, 
dry  carefully,  heat  to  a  temperature  slightly  above  100°  C.,  and  weigh  as 
antimony  trisulphide.  For  the  very  small  amounts  of  antimony  that  are 
found  in  iron  ores  this  method  is  sufficiently  exact.  The  weight  of 
antimony  trisulphide,  multiplied  by  .71390,  gives  the  weight  of  antimony. 


264  ANALYSIS    OF  IRON  ORES. 

DETERMINATION    OF    THE    ALKALIES. 

As  a  rule,  the  alkalies  in  iron  ores  are  found  exclusively  in  the  in- 
soluble silicious  matter,  and  when  the  sum  of  the  weights  of  the  silica, 
alumina,  etc.,  lime,  and  magnesia  in  the  insoluble  silicious  matter  falls  much 
below  the  weight  of  the  latter,  it  is  always  well  to  look  for  alkalies. 

Dissolve  3  grammes  of  the  ore  in  hydrochloric  acid,  evaporate  to 
dryness,  redissolve  in  10  c.c.  hydrochloric  acid  and  20  c.c.  water,  dilute, 
and  filter  into  a  platinum  dish.  Ignite  the  insoluble  residue,  treat  it  in 
the  crucible  with  hydrofluoric  acid  and  from  10  to  30  drops  sulphuric  acid, 
evaporate  down  until  the  sulphuric  acid  is  driven  off,  dissolve  in  water 
with  a  little  hydrochloric  acid  if  necessary,  transfer  to  a  small  platinum 
dish,  dilute  to  100  c.c.,  heat  to  boiling,  and  add  excess  of  barium  hy- 
droxide. Boil  for  a  few  minutes,  and  filter  from  the  alumina,  etc.,  into 
another  platinum  dish.  Evaporate  the  filtrate  to  dryness,  treat  the  resi- 
due with  a  little  water,  heat  to  boiling  and  add  ammonium  carbonate 
to  precipitate  the  barium,  filter  into  another  platinum  dish,  evaporate  to 
dryness,  and  heat  to  dull  redness.  Dissolve  in  a  few  c.c.  of  water,  and 
filter  into  a  weighed  crucible. 

Evaporate  very  low,  and,  if  nothing  separates  out,  add  a  few  drops 
of  hydrochloric  acid,  evaporate  to  dryness,  heat  to  very  dull  redness, 
cool,  and  weigh  as  potassium  chloride  -f  sodium  chloride.  To  the  resi- 
due in  the  crucible  add  a  little  water,  in  which  the  residue  should  dis- 
solve perfectly,  and  a  solution  of  platinic  chloride.  Evaporate  down  in 
the  water-bath  until  the  mass  in  the  crucible  solidifies  upon  cooling,  add 
a  little  water  to  dissolve  the  excess  of  platinic  chloride,  and  then  an 
equal  volume  of  alcohol.  Filter  on  a  Gooch  crucible,  wash  with  alcohol 
until  the  filtrate  runs  through  perfectly  colorless,  dry  at  120°  C.,  and 
weigh  as  potassium-platinic  chloride.  This  weight,  multiplied  by  .19395, 
gives  the  weight  of  potash.  Then  multiply  the  weight  of  potassium- 
platinic  chloride  by  .30696,  which  gives  the  weight  of  potassium  chloride. 
Subtract  this  from  the  weight  of  potassium  chloride  -f-  sodium  chloride 
previously  obtained,  and  the  difference  is.  the  weight  of  sodium  chloride, 
which,  multiplied  by  .53077,  gives  the  weight  of  soda. 


DETERMINATION  OF   CARBONIC  ACID.  26$ 

To  the  filtrate  from  the  insoluble  silicious  matter  add  an  excess  of 
ammonia,  rub  a  little  grease  or  paraffine  on  the  edge  of  the  dish,  and 
evaporate  the  mass  to  dryness.  This  will  render  the  ferric  oxide  very 
compact  and  granular.  Dilute  with  hot  water,  add  a  few  drops  of 
ammonia,  filter  into  another  platinum  dish,  add  a  few  drops  of  sul- 
phuric acid,  evaporate  to  dryness,  and  ignite  to  drive  off  all  the  am- 
monia salts.  Then  proceed  exactly  as  directed  for  the  determination  of 
the  alkalies  in  the  insoluble  silicious  matter.  The  alkalies  in  the  insolu- 
ble silicious  matter  may  also  be  determined  by  J.  Lawrence  Smith's 
method  of  fusion  with  calcium  carbonate  and  ammonium  chloride,  as 
directed  farther  on. 

The  ammonium  chloride,  which  is  so  troublesome  in  alkali  determi- 
nations, may  be  decomposed  *  very  easily  by  evaporating  the  solution 
down  very  low,  transferring  to  a  tall  beaker  or  flask,  and  heating  with 
a  large  excess  of  nitric  acid, — 3  or  4  c.c.  nitric  acid  to  every  gramme 
of  ammonium  chloride  supposed  to  be  present.  The  decomposition  takes 
place  at  a  temperature  below  the  boiling-point  of  water,  and  when  the 
action  seems  to  be  over,  transfer  to  a  porcelain  dish,  and  evaporate  to 
dryness  after  adding  a  few  drops  of  sulphuric  acid.  Dissolve  in  water, 
filter  into  a  platinum  dish,  and  proceed  with  the  analysis  in  the  usual 
way. 


DETERMINATION    OF    CARBONIC    ACID. 

Weigh  3  grammes  of  finely  ground  ore  into  the  flask  A  (Fig.  99), 
and  connect  the  apparatus  in  the  manner  shown  in  the  sketch.  L,  L 
are  tubulated  bottles  for  forcing  a  current  of  air  through  the  apparatus. 
The  air  is  deprived  of  any  carbonic  acid  which  it  may  contain  by  pass- 
ing through  the  tube  M,  which  is  filled  with  caustic  potash.  M  is  con- 
nected with  the  bulb-tube  B  by  the  tube  N,  a  piece  of  rubber  tubing  over 
the  slightly  tapering  end  making  an  air-tight  connection  with  B.  O  is 
a  condenser  and  serves  to  condense  the  steam  and  acid  from  the  flask 

*  J.  L.  Smith,  Am.  Jour.  Sci.  and  Art,  1871,  3d  Ser.,  i.  (whole  No.  101)  269. 


266 


ANALYSIS   OF  IRON  ORES. 


DETERMINATION  OF  COMBINED    WATER.  267 

A.  P  contains  anhydrous  cupric  sulphate,  and  Q  contains  calcium 
chloride.  The  potash-bulb  and  the  drying-tube  R  form  the  absorption 
apparatus,  and  S  is  a  safety-tube  filled  with  calcium  chloride  to  prevent 
R  from  absorbing  moisture  from  the  atmosphere.  .Weigh  the  absorption 
apparatus  with  the  precautions  mentioned  on  page  137,  and  connect  the 
apparatus.  Close  the  stopcock  C,  and  draw  a  little  air  through  the 
apparatus  by  means  of  a  piece  of  rubber  tubing  attached  to  the  end  of  S. 
Allow  the  tension  of  the  air  to  draw  the  solution  up  into  the  rear  limb 
of  the  potash-bulb,  and  if  it  remains  there  for  a  reasonable  length  of 
time  the  connections  may  be  considered  tight.  Pour  into  the  bulb  B 
10  c.c.  hydrochloric  acid  diluted  with  about  65  c.c.  water,  connect  the  tube 
N,  and  by  means  of  the  stopcock"  C  allow  the  acid  to  flow  slowly  into 
the  flask  A.  When  the  acid  has  all  run  in,  by  opening  slightly  the  stop- 
cock in  L,  start  a  slow  current  of  air  through  the  apparatus.  Warm 
the  flask  A,  gradually  increasing  the  heat  until  the  solution  boils,  and 
continue  the  application  of  heat  until  a  considerable  amount  of  water 
has  condensed  in  O.  Allow  it  to  cool  while  the  current  of  air  is  con- 
tinued, detach,  and  weigh  the  absorption  apparatus.  The  increase  of 
weight  is  the  weight  of  carbonic  acid. 


DETERMINATION    OF    COMBINED    WATER   AND    OF 
CARBON    IN    CARBONACEOUS    MATTER. 

The  ores  are  very  rare  indeed  in  which  the  combined  water  can  be 
determined  accurately  by  simply  heating  them  in  a  crucible  and  calling 
the  loss  by  ignition  "  Water  of  Composition."  Nor  is  the  method  of 
absorbing  the  moisture,  driven  off  by  heat,  in  a  drying-tube  much  more 
reliable.  The  presence  of  pyrites,  of  organic  matter,  of  graphite,  and  of 
manganese  dioxide  serves  to  complicate  the  problem.  The  water  of 
composition  may  indeed  be  determined  with  great  accuracy  by  heating 
the  ore  in  a  tube  with  lead  chromate  and  potassium  bichromate,  exactly 
as  described  for  the  determination  of  carbon  in  iron  and  steel  by  direct 
combustion  (page  143).  The  increase  of  weight  of  the  U-tube  which  is 
attached  to  the  end  of  the  combustion-tube  (and  which  in  this  case  should 


268 


ANAL  YSIS   OF  IRON  ORES. 


be  filled  with  granulated  dried  cupric  sulphate)  is  the  weight  of  "  Com- 
bined Water"  in  the  amount  of  ore  used.  By  attaching  the  absorption 
apparatus  we  likewise  obtain  the  total  carbonic  acid  in  the  ore,  or  that 
existing  as  carbonic  acid  in  the  carbonates,  and  that  due  to  the  oxida- 
tion of  any  carbon  existing  as  carbonaceous  or  organic  matter  or  as 
graphite.  By  subtracting  from  the  weight  of  carbonic  acid  thus  obtained 
the  amount  of  carbonic  acid  existing  as  carbonate  and  determined  by  .the 
method  last  given,  and  multiplying  the  difference  by  .27273,  we  get  the 

FIG.  100. 


5 
jj'NCHES 


weight  of  "  carbon  in  carbonaceous  matter."  When  it  is  necessary  to 
make  a  large  number  of  these  determinations,  the  matter  is  very  much 
simplified  by  using  the  apparatus  shown  in  Figs.  100  and  101.*  Fig.  100 
shows  the  details  of  a  form  of  tubulated  platinum  crucible  suggested  by 
Dr.  Gooch,  which  consists  of  the  crucible  with  a  flange  at  d  into  which 
fits  the  cap.  This  cap  consists  of  a  conical  cover,  H,  drawn  up  verti- 
cally into  the  tube  1.  The  horizontal  tube  J  is  burned  into  I,  and 
through  the  centre  of  I  passes  the  small  tube  K,  which,  expanding  at  a,  is 


*  Tenth  Census  of  the  United  States,  Mining  Industries,  xv.  519. 


DETERMINATION  OF  COMBINED    WATER. 


269 


burned  into  I  at  this  point,  sealing  it  securely.  The  glass  tubes  N  and  M 
are  fused  to  K  and  J  at  C  and  b  respectively.  In  analyzing  ores  con- 
taining much  water  or  carbonic  acid,  use  I  gramme;  for  others,  use  3 
grammes.  Weigh  the  finely  ground  ore,  transfer  it  to  a  small  agate 
mortar,  and  mix  it  thoroughly  with  from  7  to  10  grammes  of  previ- 
ously fused  potassium  bichromate,  transfer  it  to  the  crucible  A  (Fig.  101), 
and  place  it  in  an  air-bath  heated  to  100°  C.  to  drive  off  any  hygro- 
scopic moisture.  When  perfectly  dry,  attach  the  cap  B  to  the  crucible, 
and  stand  the  latter  in  the  triangle  C.  Close  the  end  N  with  a  piece 

FIG.  101. 


of  rubber  tubing  in  the  other  end  of  which  is  fitted  a  piece  of  glass  rod. 
Attach  the  weighed  drying-tube  D,  filled  with  calcium  chloride,  to  the 
horizontal  tube  from  B,  by  means  of  a  thoroughly  dried  velvet  cork. 
Attach  the  absorption  apparatus  E  and  F  and  the  safety-tube  G.  Fill 
the  outside  of  the  flange  d  with  small  pieces  of  fused  sodium  tungstate, 
and,  with  a  blow-pipe  flame,  melt  them,  having  previously  immersed  the 
lower  end  of  A  in  a  small  beaker  of  ice-water.  The  expansion  of  the 
air  in  the  crucible  by  the  heat  applied  to  melt  the  sodium  tungstate  will 
force  some  bubbles  through  the  potash-bulb  E,  and  the  subsequent  cool- 
ing of  the  air  in  A  will  cause  the  liquid  in  E  to  flow  back  into  the 


2/0  ANALYSIS   OF  IRON  ORES. 

rear  bulb.  If  the  difference  of  level  thus  produced  be  maintained  for 
some  minutes,  the  connections  may  be  considered  tight.  Connect  N 
with  the  bottles  L,  as  shown  in  the  sketch,  and  start  a  current  of  air 
through  the  apparatus.  The  air  is  purified  from  carbonic  acid  and 
moisture  by  passing  through  Q,  which  is  filled  with  fused  caustic  potash. 
Now,  by  means  of  the  blast-lamp  P,  heat  the  crucible  just  above  the 
top  of  the  mixture,  and  gradually  carry  the  heat  downward,  increasing 
it  at  the  same  time.  This  will  keep  the  mixture  from  frothing  and 
choking  the  tube.  Finally,  heat  the  bottom  of  the  crucible  by  the 
burner  O,  and  continue  the  application  of  the  heat  for  ten  minutes.  During 
the  whole  of  the  operation  the  air  passes  through  N  and  K  into  the 
crucible  and  out  through  J  and  M  (Fig.  100)  into  D  (Fig.  101),  and  so 
through  the  apparatus.  The  moisture  from  the  ore  should  not  be 
allowed  to  condense  in  the  wide  part  of  D  at  /,  but  should  be  driven 
forward  into  the  calcium  chloride  by  warming  the  tube  at  /  with  the 
flame  of  an  alcohol  lamp.  Allow  the  apparatus  to  cool  while  the 
current  of  air  is  continued,  then  detach,  and  weigh  the  tube  D  and  the 
absorption  apparatus,  and  calculate  the  results  as  directed  on  page  268. 
When  detached  from  the  apparatus,  the  wide  end  of  the  tube  D  may 
be  closed  by  a  short  cork,  covered  with  tin-foil  to  prevent  the  absorp- 
tion of  moisture  from  the  atmosphere.  To  clean  the  crucible,  remove  it 
from  the  stand,  and,  holding  it  in  a  piece  of  asbestos  board  in  an  inclined 
position,  melt  the  sodium  tungstate  in  the  flange  d  with  a  blow-pipe 
flame  and  detach  the  cap.  Dissolve  out  the  bichromate  by  placing  the 
crucible  in  a  dish  of  hot  water,  clean  out  the  ore,  dissolve  any  adhering 
oxide  in  hydrochloric  acid,  wash  the  crucible  and  cap  with  hot  water, 
dry  them,  and  they  will  be  ready  for  another  determination. 


DETERMINATION    OF    CHROMIUM. 

The  small  amount  of  chromium  which  is  found  in  some  iron  ores  is 
generally  converted  into  sodium  chromate  very  readily  by  fusion  with 
sodium  carbonate  and  potassium  nitrate.  Fuse  I  or  2  grammes  of  the 


DETERMINATION  OF  CHROMIUM.  2JI 

finely  ground  ore  with  ten  times  its  weight  of  sodium  carbonate  and  a 
little  potassium  nitrate.  Treat  the  fused  mass  with  water  and  wash  it 
out  into  a  small  beaker.  If  the  solution  is  colored  by  manganese,  add 
a  little  alcohol,  which  will  precipitate  the  manganese,  leaving  the  solu- 
tion, if  chromium  is  present,  slightly  yellow.  If  the  solution  is  colorless, 
it  may  be  considered  proof  of  the  absence  of  chromium.  Otherwise 
filter,  wash  the  insoluble  matter  on  the  filter,  dry  it,  grind  it  with  ten 
times  its  weight  of  sodium  carbonate  and  a  little  potassium  nitrate,  fuse, 
treat  with  water  as  before,  filter,  and  add  this  filtrate  to  the  other. 
Acidulate  the  combined  filtrates  with  hydrochloric  acid,  evaporate  to 
dryness  to  render  the  silica  insoluble,  and  reduce  the  chromic  acid  to 
chromic  oxide.  Treat  the  mass  with  hydrochloric  acid,  dilute,  filter,  and 
precipitate  the  chromic  oxide  -f-  alumina  by  ammonia.  Boil  for  some 
minutes,  filter,  wash  well  with  hot  water,  dry,  and  ignite  the  precipitate. 
Fuse  with  as  little  sodium  carbonate  and  potassium  nitrate  as  possible, 
treat  with  water,  and  wash  the  solution  into  a  platinum  dish.  Evaporate 
the  solution  until  it  is  very  concentrated,  adding  from  time  to  time 
crystals  of  ammonium  nitrate  to  change  all  the  carbonated  and  caustic 
alkali  to  nitrate.  At  each  addition  of  ammonium  nitrate  the  solution 
effervesces,  and  ammonium  carbonate  is  given  off.  When  the  solution 
is  nearly  syrupy,  the  addition  of  ammonium  nitrate  no  longer  causes  an 
effervescence,  and  the  solution  smells  faintly  of  ammonia,  add  a  few  drops 
of  ammonia,  dilute,  and  filter.  By  this  operation  all  the  alumina,  alumi- 
num phosphate,  manganese  oxide,  etc.,  are  precipitated,  and  there  remain 
in  the  solution  only  the  alkalies  and  the  alkaline  chromate.  To  the 
filtrate  add  an  excess  of  sulphurous  acid  in  water,  which  instantly 
changes  the  color  of  the  solution  from  yellow  to  green.  Boil  well, 
add  an  excess  of  ammonia,  boil  for  a  few  minutes,  filter  on  an  ashless 
filter,  wash  well  with  hot  water,  dry,  ignite,  and  weigh  as  chromic 
oxide. 

Chrome  iron  ore  is  best  decomposed  by  fusing  .5  gramme  of  very 
finely  ground  ore  with  sodium  peroxide  as  described  in  the  analysis  of 
ferro-chrome  (page  220),  and  proceeding  as  there  directed. 


2/2  ANAL  YSIS   OF  IRON  ORES. 

DETERMINATION    OF   TUNGSTEN. 

Digest  from  I  to  10  grammes  of  the  ore  in  hydrochloric  acid,  adding 
nitric  acid  from  time  to  time.  When  the  ore  appears  to  be  perfectly 
decomposed,  evaporate  to  dry  ness  on  the  water-bath  (a  higher  tempera- 
ture is  not  admissible,  as  it  may  render  the  tungstic  acid  insoluble  in 
ammonia),  redissolve  in  hydrochloric  acid,  and  evaporate  again.  Redis- 
solve  in  hydrochloric  acid,  dilute,  filter,  wash  with  acidulated  water,  and 
finally  with  alcohol.  Treat  on  the  filter  with  ammonia,  allowing  the 
filtrate  to  run  into  a  platinum  dish,  evaporate  to  small  bulk,  add 
excess  of  ammonia,  filter,  if  necessary,  into  a  platinum  crucible,  evap- 
orate carefully  to  dryness,  heat  gently  to  drive  ofT  the  ammonia,  and 
ignite.  Weigh  as  tungstic  acid. 


DETERMINATION    OF   VANADIUM. 

Fuse  5  grammes  of  very  finely  ground  ore  with  30  grammes  of 
sodium  carbonate  and  from  I  to  5  grammes  of  sodium  nitrate,  and  pro- 
ceed exactly  as  in  the  determination  of  vanadium  in  pig-iron  (page  204). 
A  second  fusion  of  the  residue  from  the  aqueous  solution  of  the  first 
fusion  is  hardly  ever  necessary. 


DETERMINATION    OF    SPECIFIC    GRAVITY. 

The  specific  gravity  of  iron  ores  is  determined  with  much  greater 
accuracy  by  employing  the  powdered  material  than  by  using  lumps  of 
the  ore.  The  little  flask  shown  in  Fig.  102  was  designed  for  this  purpose 
by  the  late  Mr.  James  Hogarth,*  and  its  use  avoids  two  difficulties 
experienced  with  the  ordinary  specific  gravity  bottle, — the  expansion  and 
overflow  consequent  upon  transferring  the  flask  at  60°  F.  to  the  higher 
temperature  of  the  balance-case,  and  the  necessity  for  waiting  until  the 
finely  divided  particles  of  the  ore  shall  have  settled  before  inserting  the 

*  Tenth  Census  of  the  United  States,  xv.  522. 


DETERMINATION  OF  SPECIFIC   GRAVITY. 


2/3 


FIG.  102. 


stopper.  These  difficulties  were  overcome  by  melting  a  capillary  tubulus 
to  the  lower  part  of  the  neck  of  the  flask,  and  by  grinding  in  a  stopper 
having  a  small  bulb  above  the  capillary,  to 
allow  for  expansion.  The  operation  of  deter- 
mining the  specific  gravity  of  an  ore  is  con- 
ducted as  follows.  Transfer  a  weighed  amount 
of  the  ore  to  the  flask,  add  enough  water  to 
cover  it,  and  heat  almost  to  the  boiling-point 
by  placing  the  flask  without  the  stopper  in  the 
water-bath.  Place  the  flask  under  a  bell-jar 
connected  with  an  aspirator  or  air-pump,  and 
expel  all  the  air  by  allowing  the  water  to  boil 
for  some  time  at  a  reduced  pressure.  Remove 
the  flask  from  the  bell-jar,  fill  it  to  the  tubulus 
with  cold  water,  insert  the  stopper,  and  cool 
the  flask  and  its  contents  to  about  60°  F.  By 
suction  on  the  stopper  draw  water  through  the 
tubulus  until  it  is  slightly  above  the  capillary 

of  the  stopper,  at  which  point  a  mark  is  scratched.  When  the  flask  and 
its  contents  are  exactly  at  60°  F.,  adjust  the  volume  exactly  to  the  mark 
on  the  capillary  by  touching  a  piece  of  blotting-paper  to  the  end  of  the 
tubulus  or  by  drawing  in  a  little  water  if  the  level  is  below  the  mark. 
Dry  the  flask,  allow  it  to  acquire  the  temperature  of  the  balance-case,  and 
weigh.  Now,  if  W  is  the  weight  of  ore  taken,  W  the  weight  of  the 
ore  and  water  at  60°  F.,  and  K  the  weight  of  the  flask  and  its  contents 
to  the  mark  of  water  at  60°  F.,  then 

W 


sp.  gr.  = 


W-f-K  — W 


To  obtain    K,  fill  the    flask  with    boiled    water,  and    treat    it    exactly  as 
described  above. 


METHODS   FOR  THE  ANALYSIS 

OF 

LIMESTONE. 


DETERMINATION  OF  INSOLUBLE  SILICIOUS  MATTER, 
ALUMINA  AND  FERRIC  OXIDE,  CALCIUM  CARBON- 
ATE, AND  MAGNESIUM  CARBONATE. 

WEIGH  I  gramme  of  the  powdered  limestone,  previously  dried  at  1 00° 
C,  place  it  in  a  No.  I  beaker,  cover  with  a  watch-glass,  and  pour  in  5 
c.c.  of  hydrochloric  acid  diluted  with  25  c.c.  of  water  and  a  little  bro- 
mine-water. Digest  on  the  hot  plate  until  all  the  action  ceases,  wash 
the  watch-glass  with  a  fine  jet  of  water,  and  evaporate  to  dryness.  Re- 
dissolve  in  10  c.c.  hydrochloric  acid  diluted  with  50  c.c.  water,  filter  on 
a  small  ashless  filter,  wash  well  with  hot  water,  dry,  ignite,  and  weigh 
as  "  Insoluble  Silicious  Matter."  Heat  the  filtrate  to  boiling,  add  a  slight 
excess  of  ammonia,  boil  for  a  few  minutes,  filter,  wash  once  or  twice. 
Dissolve  the  precipitate  on  the  filter  in  a  little  dilute  hydrochloric  acid, 
allowing  the  solution  to  run  into  the  beaker  in  which  the  precipitation 
was  made,  wash  well  with  water,  dilute,  boil,  ami  reprecipitate  by  am- 
monia. Filter  on  a  small  ashless  filter,  allow  this  filtrate  to  run  into  the 
beaker  containing  the  first  one,  wash  well  with  hot  water,  dry,  ignite, 
and  weigh  as  alumina  and  ferric  oxide.  Heat  the  united  filtrates  to 
boiling,  add  enough  ammonium  oxalate  to  convert  all  the  calcium  and 
magnesium  into  oxalates.*  Allow  the  precipitate  of  calcium  oxalate  to 
settle  for  fifteen  or  twenty  minutes,  filter  on  an  ashless  filter,  wash  with 

*  25  c.c.  of  the  saturated  solution  is  about  the  proper  quantity. 

274 


DETERMINATION  OF  LIME   AND   MAGNESIA.  2/$ 

hot  water,  dry,  ignite  for  some  time  over  a  Bunsen  burner,  and  finally 
for  fifteen  minutes  at  the  highest  temperature  of  a  blast-lamp.  Cool  in  a 
desiccator,  weigh  quickly,  ignite  again  over  the  blast-lamp  for  five  minutes, 
cool,  and  weigh  again.  If  this  weight  is  the  same,  or  nearly  the  same, 
as  the  previous  one,  call  the  amount  lime.  If  the  second  weight  is  much 
less  than  the  first,  ignite,  and  weigh  again  until  the  weight  is  constant. 
The  weight  of  lime,  multiplied  by  1.78459,  gives  the  weight  of  calcium 
carbonate.  Add  to  the  filtrate  from  the  calcium  oxalate  30  c.c.  of  a 
saturated  solution  of  microcosmic  salt  (sodium-ammonium  phosphate), 
acidulate  with  hydrochloric  acid,  and  evaporate  the  solution  to  about 
300  c.c.  If  during  the  evaporation  any  precipitate  should  separate  out, 
redissolve  it  in  hydrochloric  acid.  Cool  the  evaporated  solution  in  ice- 
water,  and  add  ammonia  drop  by  drop,  stirring  the  solution,  but  being 
careful  to  avoid  rubbing  the  sides  of  the  beaker  with  the  rod,  as  the 
precipitate  of  ammonium-magnesium  orthophosphate  is  liable  to  adhere 
with  great  tenacity  to  those  points  or  lines  where  the  rod  has  touched 
the  sides  or  bottom  of  the  beaker.  Continue  the  addition  of  ammonia 
until  the  solution  is  decidedly  alkaline,  and  then  add  an  amount  equal 
to  one-fourth  of  the  neutralized  solution.  After  the  precipitate  has  begun 
to  form,  stir  vigorously  several  times,  allow  to  stand  overnight,  filter 
on  an  ashless  filter,  rub  off  with  a  "policeman"  any  of  the  precipitate 
that  may  adhere  to  the  beaker,  wash  with  a  mixture  of  I  part  ammonia 
and  2  parts  water,  containing  100  grammes  of  ammonium  nitrate  to  the 
litre,  dry,  ignite  with  great  care,  as  directed  on  page  250,  cool,  and 
weigh  as  magnesium  pyrophosphate,  which,  multiplied  by  .36212,  gives 
the  weight  of  magnesia,  and,  multiplied  by  .75760,  gives  the  weight  of 
magnesium  carbonate. 

Limestones,  besides  the  ordinary  constituents  mentioned  above,  may 
contain  small  amounts  of  phosphoric  acid,  sulphur  as  sulphate  or  as 
pyrites,  titanic  acid,  organic  matter,  combined  water,  alkalies,  manganese, 
fluorine,  and  in  rare  instances  nearly  all  the  metals  found  in  iron  ores. 
For  most  of  these  the  methods  described  in  the  analysis  of  iron  ores 
may  be  employed.  Very  often  the  amounts  of  silica  and  alumina  are 
required  in  calculating  mixtures  for  the  blast-furnace,  and,  as  the  matter 


2/6  ANALYSIS   OF  LIMESTONE. 

insoluble  in  hydrochloric  acid  consists  usually  of  alumina,  lime,  and  mag- 
nesia silicates,  it  would  be  necessary  in  accurate  work  to  decompose  the 
"  Insoluble  Silicious  Matter"  by  fusion  with  sodium  carbonate  and  to  make 
a  separate  analysis  of  it,  as  described  on  page  249.  It  is,  indeed,  much 
better  to  make  the  analysis  in  this  way  than  to  add  the  filtrate  from 
the  silica  to  the  main  solution,  for  the  calcium  oxalate  is  sure  to  carry 
down  some  of  the  sodium  salts  with  it  and  thus  very  materially  com- 
plicate the  analysis. 

After  weighing  the  alumina  and  ferric  oxide  from  the  "  Insoluble  Sili- 
cious Matter"  and  that  from  the  portion  soluble  in  dilute  hydrochloric  acid 
to  determine  the  ferric  oxide,  fuse  the  two  precipitates  with  a  little  sodium 
carbonate,  dissolve  in  water,  transfer  to  a  beaker  and  acidulate  with  hy- 
drochloric acid,  add  a  few  small  crystals  of  citric  acid  to  the  clear  solution, 
then  excess  of  ammonia  and  ammonium  sulphide.  Allow  the  precipitate 
of  ferrous  sulphide  to  settle,  filter,  wash  slightly,  dissolve  in  hydrochloric 
acid,  add  a  little  bromine-water,  boil  the  solution,  precipitate  by  am- 
monia, filter,  wash,  ignite,  and  weigh  as  ferric  oxide.  The  weight  of 
ferric  oxide  subtracted  from  the  weight  of  the  total  alumina  -f  ferric 
oxide  gives,  of  course,  the  weight  of  alumina. 

The  lime  and  magnesia  in  the  "  Insoluble  Silicious  Matter"  should  not 
be  calculated  as  carbonates,  but  should  be  considered  as  existing  as  lime 
and  magnesia. 

To  determine  phosphoric  acid  in  limestones,  treat  20  grammes  with 
dilute  hydrochloric  acid,  filter  from  the  insoluble  silicious  matter,  to 
the  filtrate  add  a  few  drops  of  ferric  chloride  solution,  then  ammonia 
until  the  solution  is  alkaline  to  litmus-paper,*  and  acetic  acid  to  decided 
acid  reaction.  Boil  for  a  few  minutes,  filter,  wash  once  with  hot  water, 
dissolve  in  hydrochloric  acid  on  the  filter,  allowing  the  solution  to  run 
into  the  beaker  in  which  the  precipitation  was  made,  add  the  solution 
from  the  treatment  of  the  insoluble  silicious  matter  mentioned  below, 
dilute,  and  reprecipitate  exactly  as  before  with  ammonia  and  acetic  acid. 


*  If  the  precipitate  is  not  decidedly  red  in  color,  acidulate  with  hydrochloric  acid  and  add  more 
ferric  chloride  solution. 


DETERMINATION  OF  SULPHUR.  2 77 

Dissolve  this  precipitate  on  the  filter  in  dilute  hydrochloric  acid,  allowing 
the  solution  to  run  into  a  No.  I  beaker,  wash  the  filter  with  hot  water, 
evaporate  the  solution  down  almost  to  dryness,  and  precipitate  the  phos- 
phoric acid  as  directed  on  page  80  et  seq. 

Ignite  the  insoluble  silicious  matter  with  hydrofluoric  acid  and  a  few 
drops  of  sulphuric  acid,  evaporate  until  fumes  of  sulphuric  anhydride  are 
given  off,  fuse  with  sodium  carbonate,  digest  in  water,  filter,  acidulate  the 
solution  with  hydrochloric  acid?  and  add  it  to  the  solution  of  the  first 
precipitate  in  the  soluble  portion  as  mentioned  above. 

Instead  of  treating  the  insoluble  silicious  matter  with  hydrofluoric 
and  sulphuric  acids,  it  may  be  fused  at  once  with  sodium  carbonate,  the 
fused  mass  treated  with  water,  filtered,  the  filtrate  acidulated,  evaporated  to 
dryness,  redissolved  in  water  slightly  acidulated  with  hydrochloric  acid, 
filtered,  and  the  filtrate  added  to  the  solution  of  the  first  precipitate  by 
ammonia  and  acetic  acid  as  above. 

To  determine  sulphur  in  limestone,  fuse  I  gramme  with  sodium  car- 
bonate and  potassium  nitrate  exactly  as  in  the  determination  of  sulphur 
in  iron  ores  (page  237  et  seq.). 

To  determine  sulphates,  proceed  as  in  the  analysis  of  iron  ores  for  these 
substances  (page  238). 


METHODS   FOR  THE  ANALYSIS 


OF 


CLAY. 


CLAY  is  essentially  silica,  mixed  with  aluminum,  calcium,  magnesium, 
potassium,  and  sodium  silicates.  These  silicates  are  hydrated,  so  that  clay 
usually  contains  from  6  to  12  per  cent,  of  water  of  composition.  Besides 
these  usual  constituents,  clay  may  contain  ferric  oxide,  titanic  acid,  pyrites, 
organic  matter,  phosphoric  acid,  and  occasionally  some  of  the  rarer 
elements,  such  as  vanadium. 

Clay  being  practically  unacted  on  by  hydrochloric  acid,  it  is  necessary 
to  proceed  as  follows.  Fuse  I  gramme  of  the  finely  ground  clay,  dried  at 
100°  C,  with  10  grammes  of  sodium  carbonate  and  a  very  little  sodium 
nitrate.  Run  the  fused  mass  well  up  on  the  sides  of  the  crucible,  allow  it 
to  cool,  and  treat  it  with  hot  water  until  thoroughly  disintegrated,  transfer- 
ring the  liquid  from  time  to  time  to  a  platinum  dish.  Treat  the  crucible 
with  hydrochloric  acid,  add  this  to  the  liquid  in  the  dish,  acidulate  with 
hydrochloric  acid,  and  evaporate  to  diyness  in  the  air-bath.  Treat  the 
mass  with  water  and  a  little  hydrochloric  acid,  evaporate  again  to  dryness, 
and  treat  with  15  c.c.  hydrochloric  acid  and  45  c.c.  water.  Allow  it  to 
stand  in  a  warm  place  for  fifteen  or  twenty  minutes,  add  50  c.c.  water,  and 
filter  on  an  ashless  filter.  Wash  thoroughly  with  hot  water  acidulated  with 
a  few  drops  of  hydrochloric  acid,  dry,  ignite,  heat  for  three  or  four  minutes 
over  the  blast-lamp,  and  weigh.  Treat  the  precipitate  with  hydrofluoric 
acid  and  a  few  drops  of  sulphuric  acid,  evaporate  to  dryness,  ignite,  and 
278 


DETERMINATION  OF  ALKALIES.  279 

weigh.  The  difference  between  the  two  weights  is  silica.  If  any  appreci- 
able residue  remains  in  the  crucible,  treat  it  with  a  little  hydrochloric  acid, 
and  wash  it  out  into  the  filtrate  from  the  silica.  Transfer  the  filtrate  from 
the  silica  to  a  large  platinum  dish,  heat  it  to  boiling,  add  an  excess  of 
ammonia,  boil  until  the  smell  of  ammonia  is  quite  faint,  filter  on  an  ashless 
filter,  and  wash  several  times  with  hot  water.  Stand  the  filtrate  and  wash- 
ings aside,  and  treat  the  precipitate  on  the  filter  with  a  mixture  of  15  c.c. 
hydrochloric  acid  and  1 5  c.c.  water  (cold).  Allow  the  solution  to  run  into  a 
small  clean  beaker,  replace  this  by  the  platinum  dish  in  which  the  pre- 
cipitation was  made,  pour  the  solution  on  the  filter  again,  and  repeat 
this  operation  until  the  precipitate  has  completely  dissolved.  Rinse  the 
beaker  and  wash  the  filter  thoroughly  with  cold  water,  dry,  and  pre- 
serve it.  Reprecipitate  by  ammonia,  as  above  directed,  filter  on  an  ashless 
filter,  wipe  the  dish  with  small  pieces  of  filter-paper,  add  these  to  the 
precipitate,  and  wash  thoroughly  with  hot  water.  Dry,  ignite  the  pre- 
cipitate and  filter,  and  the  filter  from  the  first  precipitation,  heat  for  a  few 
minutes  over  the  blast-lamp,  cool,  and  weigh  as  alumina  and  ferric  oxide. 
Fuse  the  ignited  precipitate  with  sodium  carbonate,  treat  the  fused  mass 
with  water,  wash  it  into  a  small  beaker,  allow  the  residue  to  settle, 
decant  off  the  clear,  supernatant  fluid,  treat  the  residue  with  hydrochloric 
acid,  and  determine  the  iron  volu metrically,  or  add  citric  acid  and  ammonia, 
and  after  precipitating  the  iron  as  sulphide,  filter,  wash,  dissolve  in  hydro- 
chloric acid,  oxidize  with  bromine-water,  and  precipitate  the  ferric  oxide 
by  ammonia.  Filter,  wash,  dry,  ignite,  and  weigh  as  ferric  oxide.  Sub- 
tract the  weight  of  ferric  oxide  from  the  alumina  +  ferric  oxide  found 
above,  and  the  difference  is  alumina. 

As  the  amounts  of  calcium  and  magnesium  in  clay  are  very  small, 
the  filtrate  and  washings  from  the  second  precipitation  of  alumina  +  ferric 
oxide  may  be  rejected  and  the  lime  and  magnesia  determined  in  the  first 
filtrate  as  directed  on  page  275. 

To  determine  the  alkalies  in  clay,  treat  2  grammes  of  the  finely  ground 
material  in  a  platinum  dish  with  4  c.c.  of  strong  sulphuric  acid  and  40  or 
50  c.c.  of  redistilled  hydrofluoric  acid.  Stir  it  from  time  to  time  with  a 
platinum  wire  or  rod,  heating  carefully,  until  the  clay  is  entirely  decom- 


2  So  A  ANALYSIS   OF  CLAY. 

posed  and  no  more  gritty  substance  can  be  felt  under  the  rod.  Evaporate 
to  dryness,  and  heat  until  no  more  fumes  of  sulphuric  anhydride  are  given 
off.  The  entire  operation  should  be  carried  on  under  a  hood  with  a  good 
draft,  as  hydrofluoric  acid  is  poisonous,  and  the  evaporation  may  safely  be 
conducted  on  the  little  arrangement  shown  in  Fig.  10,  page  20.  Allow 
the  dish  to  cool,  add  about  50  c.c.  water  and  a  little  hydrochloric  acid,  and 
heat  until  the  mass  is  all  dissolved.  If  any  of  the  clay  has  escaped  decom- 
position, filter  into  another  platinum  dish,  wash  the  insoluble  matter  on 
the  filter,  dry,  ignite,  and  decompose  it  in  the  crucible  with  hydrofluoric 
and  sulphuric  acids.  Dissolve  the  mass  in  the  crucible  after  evaporating 
off  the  hydrofluoric  and  sulphuric  acids,  and  add  the  solution  to  the  main 
solution  in  the  dish.  Dilute  this  solution  to  300  or  400  c.c.  with  hot  water, 
heat  to  boiling,  add  an  excess  of  barium  hydrate,  boil  for  a  few  minutes, 
and  filter.  Allow  the  precipitate  to  drain  well  on  the  filter,  remove  the 
filtrate,  which  should  be  in  a  platinum  dish,  to  a  light,  and  evaporate  it 
down.  Pierce  the  filter  with  a  wire  or  rod,  and  wash  the  precipitate  into 
the  dish  in  which  the  precipitation  was  made  with  a  jet  of  hot  water. 
Dilute  to  300  or  400  c.c.,  heat  to  boiling,  filter,  and  wash  several  times 
with  hot  water.  Add  this  filtrate  to  the  first  one,  evaporate  to  dryness, 
and  proceed  exactly  as  directed  for  the  determination  of  alkalies  in  the 
"  Insoluble  Silicious  Matter"  from  iron  ores  (page  264). 

Instead  of  decomposing  the  clay  with  hydrofluoric  and  sulphuric  acids, 
the  method  given  by  J.  Lawrence  Smith  may  be  used  for  determining 
alkalies.  Place  I  gramme  of  the  finely  ground  clay  in  a  porcelain  or  agate 
mortar,  add  an  equal  weight  of  granular  ammonium  chloride,*  and  grind 
the  two  together  to  mix  them.  Add  8  grammes  of  calcium  carbonate,f 
and  grind  the  entire  mass  so  as  to  obtain  an  intimate  mixture  of  the  whole. 
Transfer  to  a  capacious  platinum  crucible,  cover  with  a  close-fitting  lid,  and 
heat  carefully  to  decompose  the  ammonium  chloride,  which  is  accomplished 
in  a  few  minutes.  Heat  gradually  to  redness,  and  keep  the  bottom  of  the 
crucible  at  a  bright  red  for  about  an  hour.  Allow  the  crucible  to  cool,  and 
if  the  mass  is  easily  detached  from  the  crucible,  transfer  it  to  a  platinum 


*  See  page  45.  f  See  page  52. 


DETERMINATION  OF  TITANIC  ACID.  28 1 

dish  and  add  about  80  c.c.  of  water.  Wash  the  crucible  and  lid  with 
boiling  water,  pouring  washings  into  the  dish.  Heat  the  water  in  the  dish 
to  boiling,  and,  when  the  mass  has  completely  slaked,  filter  into  another 
platinum  dish  and  wash  the  mass  on  the  filter  with  hot  water.  If  the 
semi-fused  mass  in  the  crucible  is  not  easily  detached,  place  the  crucible 
on  its  side  in  the  dish,  add  about  100  c.c.  water,  and  heat  until  the  mass 
disintegrates.  Remove  the  crucible,  rinse  it,  and  filter  as  above  directed. 
To  the  filtrate  add  about  \]/2  grammes  of  pure  ammonium  carbonate, 
evaporate  on  the  water-bath,  or  very  carefully  over  a  light,  until  the 
volume  of  the  solution  is  reduced  to  about  40  c.c.,  add  a  little  more 
ammonium  carbonate  and  a  few  drops  of  ammonia,  and  filter  on  a 
small  filter.  Evaporate  the  filtrate  carefully  after  adding  a  few  drops 
more  of  ammonium  carbonate  to  make  certain  that  all  the  lime  has 
been  precipitated.  If  any  further  precipitate  appears,  filter  into  a 
platinum  crucible  and  evaporate  to  dryness.  Heat  carefully  to  dull 
redness  to  drive  off  any  ammonium  salts,  and  weigh  the  residue  as 
potassium-sodium  chloride.  Separate  the  potash  and  soda  as  directed 
on  page  264. 

Determine  the  water  of  composition  by  igniting  I  gramme  of  the  clay 
for  twenty  minutes  at  a  bright  red  heat,  when  the  loss  of  weight  will  repre- 
sent the  water.  In  the  presence  of  much  organic  matter  or  pyrites  the 
method  given  for  the  determination  of  water  of  composition  in  iron  ores 
(page  267)  may  be  used. 

To  determine  titanic  acid,  treat  2  grammes  of  the  finely  ground  clay  in 
a  large  platinum  crucible  with  hydrofluoric  acid  and  5  c.c.  sulphuric  acid. 
Evaporate  off  the  hydrofluoric  acid  and  heat  carefully  until  the  greater  part 
of  the  sulphuric  acid  is  volatilized.  Allow  the  crucible  to  cool,  add  10 
grammes  of  sodium  carbonate,  and  fuse  for  thirty  minutes  at  the  highest 
temperature  obtainable  by  a  Bunsen  burner.  Run  the  fused  mass  well  up 
on  the  sides  of  the  crucible,  and  allow  it  to  cool.  Treat  the  fused  mass 
with  water,  transfer  it  to  a  beaker,  and  filter.  Wash  the  insoluble  matter 
slightly  on  the  filter,  dry,  ignite,  and  fuse  it  again  with  sodium  carbonate. 
Dissolve  in  water  as  before,  and  filter.  By  this  method  of  treatment  nearly 
all  of  the  alumina  will  be  dissolved  and  separated  from  the  titanic  acid. 


282  ANALYSIS    OF  CLAY. 

Fuse  the  insoluble  matter   left  on   the  filter  with  sodium  carbonate,  and 
determine  the  titanic  acid  as  directed  on  page  241. 

When  alkalies  are  determined,  the  precipitated  alumina  may  be  used 
for  the  determination  of  titanic  acid.  In  this  case  dry  the  precipitate 
of  alumina,  etc.,  separate  it  from  the  filter,  ignite  the  two  filters,  add  the 
ash  to  the  dried  (not  ignited)  precipitate  of  alumina,  etc.,  and  fuse  with 
sodium  carbonate  as  above. 


METHODS   FOR  THE  ANALYSIS 


OF 


SLAGS. 


BLAST-FURNACE  slags  contain  silica,  alumina,  lime,  magnesia,  and  alka- 
lies always,  generally  also  ferrous  oxide,  manganous  oxide,  and  sulphur, 
and  occasionally  titanic  acid,  small  amounts  of  phosphoric  acid,  and  such 
metallic  oxides  as  may  exist  in  the  ores,  fluxes,  or  fuel  used  in  the  furnace. 
Sulphur,  which  is  occasionally  present  in  considerable  amounts,  is  consid- 
ered to  exist  in  the  slag  as  calcium  sulphide. 

The  method  used  for  the  determination  of  the  principal  ingredients 
depends  upon  whether  the  slag  is  capable  of  being  entirely  or  but  partially 
decomposed  by  hydrochloric  acid. 

In  the  first  case  weigh  I  gramme  of  the  finely  ground  slag,  place  it  in  a 
platinum  or  porcelain  dish,  add  20  c.c.  of  water,  and  shake  the  dish  until 
the  material  is  thoroughly  disseminated  through  the  water.  Add  gradually 
30  c.c.  hydrochloric  acid,  with  constant  stirring,  and  finally  heat  the  dish 
carefully.  The  slag  will  dissolve  completely  to  a  clear  liquid,  but,  after 
heating  for  a  short  time,  will  suddenly  form  a  solid  jelly.  Evaporate  care- 
fully to  dryness,  treat  with  a  few  c.c.  of  dilute  hydrochloric  acid  and  a  little 
bromine-water,  evaporate  again  to  dryness,  and  add  15  c.c.  hydrochloric 
acid  and  45  c.c.  water.  Allow  to  stand  fifteen  or  twenty  minutes  in  a  warm 
place,  add  50  c.c.  water,  filter  on  an  ashless  filter,  wash  thoroughly  with  hot 
water,  dry,  ignite,  and  weigh.  Treat  the  material  in  the  crucible  with  a 
little  water,  add  2  or  3  drops  sulphuric  acid  and  enough  hydrofluoric  acid 
to  dissolve  it.  Evaporate  to  dryness,  ignite,  and  weigh.  The  loss  of 
weight  is  silica. 

283 


284  ANALYSIS   OF  SLAGS. 

Any  residue  in  the  crucible  after  the  volatilization  of  the  silica  is  to  be 
added  to  the  alumina  and  ferric  oxide.  Heat  the  filtrate  obtained  above, 
diluted  to  500  c.c.,  to  boiling,  add  a  slight  excess  of  ammonia,  boil  for  a 
few  minutes,  filter  on  an  ashless  filter,  and  wash  two  or  three  times  with 
boiling  water.  Stand  the  filtrate  aside,  and  pour  on  the  precipitate  in  the 
filter  a  mixture  of  15  c.c.  hydrochloric  acid  and  30  c.c.  cold  water,  allowing 
the  solution  to  run  into  the  dish  in  which  the  precipitation  was  made. 
Alumina  precipitated  in  this  way  seems  generally  to  dissolve  more  readily 
in  cold  than  in  hot  dilute  hydrochloric  acid,  but  it  is  often  necessary  to 
break  up  the  precipitate  on  the  filter  with  a  rod,  and  pour  the  acid  solution 
back  on  the  filter  several  times  after  it  has  run  through,  or  sometimes  to 
pierce  the  filter  with  a  rod  or  wire  and  wash  the  precipitate  still  undissolved 
into  the  dish.  Wash  the  filter  well  with  water,  dry  it,  and  keep  it  to  ignite 
with  the  alumina,  etc.  Heat  the  filtrate  and  washings  to  boiling,  reprecipi- 
tate  by  ammonia,  filter  on  an  ashless  filter,  clean  off"  any  adhering  precipi- 
tate from  the  dish  with  filter-paper,  add  it  to  the  precipitate  on  the  filter, 
wash  well  with  hot  water,  dry,  ignite,  after  adding  the  filter  on  which  the 
first  precipitation  was  filtered,  and  weigh  as  alumina,  etc.  Add  to  this  the 
weight  of  the  residue  from  the  treatment  of  the  silica  by  sulphuric  and 
hydrofluoric  acids,*  and  the  sum  is  the  total  alumina  -f-  ferric  oxide  -f- 
phosphoric  acid  -f  titanic  acid. 

Evaporate  the  two  filtrates  obtained  above  down  to  about  300  c.c.,  trans- 
fer to  a  No.  3  beaker,  add  a  few  drops  of  ammonia  and  enough  ammonium 
sulphide  to  precipitate  the  manganese.  Filter  off  and  determine  the  man- 
ganese as  directed  on  page  244,  in  the  "  Analysis  of  Iron  Ores."  To  the 
filtrate  from  the  manganese  sulphide  add  a  slight  excess  of  hydrochloric 
acid,  boil  until  all  the  hydrogen  sulphide  is  driven  off,  filter  from  any  pre- 
cipitated sulphur,  and  determine  the  lime  and  magnesia  as  directed  on  page 
275  et  seq.,  in  the  "  Analysis  of  Limestone." 

To  determine  the  ferrous  oxide,  fuse  the  ignited  precipitate  of  alumina, 
etc.,  obtained  above,  with  5  grammes  of  sodium  carbonate,  at  a  very  high 
temperature,  for  at  least  thirty  minutes.  Allow  the  crucible  to  cool,  treat 

*  This  residue  should  be  examined  for  lime. 


DETERMINATION  OF  PHOSPHORIC  ACID.  285 

the  fused  mass  with  water,  transfer  to  a  beaker,  allow  the  insoluble  matter 
to  settle,  decant  the  clear,  supernatant  liquid  through  a  filter,  and  treat  the 
residue  with  hydrochloric  acid.  Pour  the  solution  through  the  filter  to  take 
up  any  iron  that  may  have  been  suspended  in  the  liquid  decanted  through 
it,  and  determine  the  iron  volumetrically  or  by  precipitation  as  sulphide  in 
the  solution  to  which  citric  acid  and  an  excess  of  ammonia  have  been  added, 
as  on  page  257.  When  the  slag  contains  no  appreciable  amount  of  man- 
ganese, the  precipitation  by  ammonium  sulphide  (page  284)  may  be  omitted 
and  the  lime  precipitated  at  once  from  the  concentrated  solution. 

For  the  analysis  of  slags  that  are  not  entirely  decomposed  by  hydro- 
chloric acid,  recourse  must  be  had  to  fusion  with  sodium  carbonate  and  a 
little  sodium  nitrate,  exactly  as  described  for  the  analysis  of  clay  (page  278 
et  seg.).  After  filtering  off  the  silica  as  directed  (page  278),  proceed  with  the 
analysis  as  described  for  slags  decomposed  by  hydrochloric  acid  (page  283 
et  seg.).  As,  however,  the  calcium  oxalate  is  very  liable  to  carry  down 
sodium  salts  with  it,  it  is  always  well,  after  igniting  the  calcium  oxalate,  to 
dissolve  it  in  dilute  hydrochloric  acid,  transfer  the  solution  to  a  platinum 
dish,  dilute  to  300  c.c.  with  hot  water,  add  an  excess  of  ammonia,  and  pre- 
cipitate boiling  by  30  c.c.  of  a  saturated  solution  of  ammonium  oxalate. 
Filter,  wash,  ignite,  and  weigh  in  the  usual  manner. 

For  the  determination  of  sulphur  in  slags,  fuse  I  gramme  with  sodium 
carbonate  and  a  little  potassium  nitrate,  and  proceed  exactly  as  directed  for 
the  determination  of  sulphur  in  iron  ores  (page  237  et  seq^.  Calculate  the 
total  sulphur  as  calcium  sulphide  and  the  remainder  of  the  calcium  as 
lime. 

For  the  determination  of  alkalies,  titanic  acid,  etc.,  proceed  as  directed 
for  the  determination  of  these  substances  in  clay. 

Converter  slags,  open-hearth  slags,  refinery  slag,  tap  cinder,  mill  cinder, 
etc.,  are  analyzed  by  the  methods  described  for  the  analysis  of  iron 
ores.  In  the  case  of  slags  obtained  from  the  manufacture  of  steel  by  the 
basic  process,  which  usually  contain  very  large  amounts  of  phosphoric 
acid,  proceed  as  follows.  Treat  I  gramme  of  the  finely  ground  slag  in  a 
small  beaker  with  15  c.c.  hydrochloric  acid  and  a  little  nitric  acid  until  it  is 
decomposed.  Evaporate  to  dry  ness,  redissolve  in  10  c.c.  hydrochloric  acid 


286  ANALYSIS   OF  SLAGS. 

and  20  c.c.  water,  dilute,  filter,  and  weigh  the  silica.  To  the  filtrate  di- 
luted to  500  C-C.  add  a  solution  of  ferric  chloride  and  a  slight  excess  of 
ammonia,  if  the  precipitate  is  not  decidedly  red  in  color,  acidulate  carefully 
with  hydrochloric  acid,  add  more  ferric  chloride  solution,  and  then  a  slight 
excess  of  ammonia.  Add  acetic  acid  to  slight  acid  reaction,  heat  to  boil- 
ing, filter  and  wash  slightly  with  boiling  water,  stand  the  filtrate  aside,  and 
dissolve  the  precipitate  on  the  filter  in  hydrochloric  acid,  allow  the  solution 
to  run  into  the  beaker  in  which  the  precipitation  was  made,  wash  the  filter 
thoroughly  with  cold  water,  dilute  the  filtrate  to  about  400  c.c.,  add  a  slight 
excess  of  ammonia  and  then  acetic  acid,  boil,  and  filter  as  before.  Add 
this  filtrate  to  the  first,  evaporate  down,  and  determine  the  manganese, 
lime,  and  magnesia,  as  directed  in  the  case  of  blast-furnace  slags  (page 
284).  Dissolve  the  precipitate  on  the  filter  in  hydrochloric  acid,  dissolving 
any  iron  that  may  adhere  to  the  beaker  in  a  few  drops  of  the  same  acid, 
pour  it  on  the  filter,  and  wash  the  beaker  and  filter  well  with  water.  Allow 
the  solution  and  washings  to  run  into  a  No.  3  beaker,  and  add  about  10 
grammes  of  citric  acid  and  an  excess  of  ammonia.  To  this  solution,  which 
should  be  cold,  and  should  measure  about  300  c.c.,  add,  drop  by  drop,  50 
c.c.  of  magnesia-mixture,  stirring  carefully,  without  touching  the  sides  of 
the  beaker  with  the  rod.  Add  about  one-third  the  volume  of  the  solution 
of  ammonia,  allow  the  beaker  to  stand  in  ice-water  for  some  time,  stir  vig- 
orously several  times,  and  after  a  few  hours  filter  (preferably  on  a  Gooch 
crucible),  wash  with  ammonia-water  of  the  usual  strength,  ignite  carefully, 
and  weigh  as  magnesium  pyrophosphate.  Any  alumina  in  the  slag  will 
be  in  the  filtrate  from  the  ammonium-magnesium  phosphate,  and  may  be 
determined  by  the  method  on  page  257.  Determine  the  iron  volumetrically 
in  a  separate  portion,  and  calculate  to  ferrous  oxide.  Determine  any  other 
elements  present  by  the  methods  under  "  Analysis  of  Iron  Ores." 

Phosphoric  acid  cannot  well  be  determined  in  basic  slags  by  fusion  with 
sodium  carbonate,  as  calcium  phosphate  is  not  readily  decomposed  by  this 
method,  and  its  employment  may  lead  to  error. 


METHOD  FOR  THE  ANALYSIS 

OF 

FIRE-SANDS. 


As  sand  contains  comparatively  very  small  amounts  of  alumina,  lime, 
and  magnesia,  and  a  very  large  amount  of  silica,  it  is  best  to  proceed  with 
the  analysis  as  follows.  Place  2  grammes  of  the  finely  ground  sand  in  a 
large,  platinum  crucible,  moisten  it  with  cold  water,  add  6  or  8  drops  of 
sulphuric  acid,  and  then  gradually  enough  hydrofluoric  acid  to  dissolve  it. 
Evaporate  to  dryness  (under  a  hood,  of  course),  and  heat  to  redness  to 
drive  off  the  sulphuric  acid.  Allow  the  crucible  to  cool,  add  a  little  sodium 
carbonate,  and  fuse.  Dissolve  the  fusion,  when  cold,  in  water,  add  an  excess 
of  hydrochloric  acid,  evaporate  to  dryness,  redissolve  in  hydrochloric  acid 
and  water,  filter  from  silica,  and  determine  the  alumina,  lime,  and  magnesia 
as  usual.  Ignite  I  gramme  of  the  sand  and  determine  the  loss,  which  will 
be  water  and  organic  matter  (if  present). 

It  is  well  to  note  that  in  the  presence  of  alumina  it  is  almost  impossible 
to  drive  off  all  the  silica  by  treatment  with  hydrofluoric  and  sulphuric 
acids,  and  the  small  amount  of  silica  remaining  after  this  treatment  must  be 
separated  as  directed  above. 

Add  together  the  percentages  of  water,  alumina,  lime,  and  magnesia, 
subtract  the  sum  from  100,  and  call  the  remainder  silica. 


287 


METHODS   FOR  THE  ANALYSIS 

OF 

COAL  AND  COKE. 


A  PROXIMATE  analysis  affords  a  very  rapid  and  comparatively  simple 
way  of  classifying  and  valuing  coal.  From  the  nature  of  the  material,  the 
determinations  cannot  be  absolute,  but  inferences  may  be  drawn  from  the 
relative  proportions  of  Moisture,  Volatile  Combustible  Matter,  and -Ash. 
Therefore  it  is  essential  that  the  analysis  should  be  performed  in  such  a 
way  as  to  obtain  the  most  concordant  results. 


PROXIMATE    ANALYSIS.* 

Determination  of  Moisture. 

"  Dry  one  gramme  of  the  coal  in  an  open  porcelain  or  platinum  crucible 
at  from  104°  to  107°  C.  for  one  hour,  best  in  a  double-walled  bath  contain- 
ing pure  toluene.f  Cool  in  a  desiccator  and  weigh  covered. 

"  With  coals  high  in  moisture,  and  in  all  cases  where  accuracy  is  desired, 
determinations  must  be  made  both  with  the  coarsely  ground  and  with  the 
powdered  coal.  When,  as  will  usually  be  the  case,  more  moisture  is  found 
in  the  coarsely  ground  than  in  the  powdered  coal,  a  correction  must  be 
applied  to  all  determinations  made  with  the  latter.  Thus,  if  I  per  cent. 

*  From  the  Report  of  the  Committee  on  Coal  Analysis  to  the  American  Chemical  Society, 
Journal  of  the  American  Chem.  Soc.,  xxi.  1116.  William  A.  Noyes,  W.  F.  Hillebrand,  and  C. 
B.  Dudley,  committee. 

f  Victor  Meyer,  Ber.  d.  Chem.  Ges.,  17,  2999. 
288 


PROXIMATE  ANALYSIS.  289 

more  of  moisture  is  found  in  the  coarsely  ground  sample,  a  total  of  I  per 
cent,  must  be  subtracted  from  the  quantities  of  the  other  constituents  as 
determined  with  the  powdered  sample.  Or,  in  the  form  of  a  rule  :  divide 
the  difference  in  moisture  by  the  per  cent,  of  other  constituents  than 
moisture  as  found  in  the  powdered  coal  by  the  quotient  and  subtract  the 
resulting  product  from  the  amount  of  the  given  constituent. 
"  Thus,  suppose  the  results  of  an  analysis  give : 

Coarsely  ground      Powdered 
Coal.  Coal. 

Moisture 12.07  IO-39 

Volatile  combustible  matter 34-25f 

then  the  correction  factor  will  be 

.3.07 -. 0.39  =;  ^68  = 

100  —  10.39       89.61 

and  the  true  per  cent,  of  volatile  combustible  matter  will  be 
34.25  —  (34.25  x  0.0187)  ==  33.61. 

"  It  is  possible  that  volatile  combustible  matter  and  ash  may  be  deter- 
mined with  the  coarsely  ground  coal  without  serious  error,  but  we  have  not 
enough  data  at  our  command  to  warrant  such  a  recommendation. 

"  The  toluene  bath  is  recommended  for  convenience,  but  any  other  bath 
at  the  proper  temperature  will  answer  equally  well.  In  all  cases  recorded 
below  the  coals  gained  in  weight,  probably  from  oxidation,  after  one  hour's 
heating,  so  that  longer  heating  is  not  only  unnecessary  but  undesirable. 
A  higher  temperature  appears  also  to  be  undesirable." 

Determination  of  Volatile  Combustible  Matter. 
"  Place  i  gramme  of  fresh,  undried,  powdered  coal  in  a  platinum 
crucible  weighing  20  or  30  grammes  and  having  a  tightly  fitting 
cover.  Heat  over  the  full  flame  of  a  Bunsen  burner  for  seven  minutes. 
The  crucible  should  be  supported  on  a  platinum  triangle  with  the  bottom 
from  6  to  8  cm.  above  the  top  of  the  burner.  The  flame  should  be  fully 
20  cm.  high  when  burning  free,  and  the  determination  should  be  made 
in  a  place  free  from  draughts.  The  upper  surface  of  the  cover  should  burn 

clear,  but  the  under  surface  should  remain  covered  with  carbon.     To  find 

19 


2QO  ANALYSIS    OF  COAL   AND    COKE. 

Volatile  Combustible  Matter,  subtract  the  per  cent,  of  moisture  from  the 
loss  found  here."  (The  weight  of  the  material  left  in  the  crucible  is 
"  coke.") 

Determination  of  Ash. 

"  Burn  the  portion  of  powdered  coal  used  for  the  determination  of 
moisture,  at  first  over  a  very  low  flame,  with  the  crucible  open  and 
inclined,  till  free  from  carbon.  If  properly  treated,  this  sample  can  be 
burned  much  more  quickly  than  the  dense  carbon  left  from  the  deter- 
mination of  volatile  matter.  It  is  advisable  to  examine  the  ash  for 
unburned  carbon  by  moistening  it  with  alcohol. 

"  When  the  sulphur  in  the  coal  is  in  the  form  of  pyrites,  that  compound 
is  converted  almost  entirely  into  ferric  oxide  in  the  determination  of  ash;  and, 
since  three  atoms  of  oxygen  replace  four  atoms  of  sulphur,  the  weight  of  the 
ash  is  less  than  the  weight  of  the  mineral  matter  in  the  coal  by  five-eighths 
of  the  weight  of  the  sulphur.  While  the  error  from  this  source  is  some- 
times considerable,  the  committee  does  not  recommend  such  a  correction 
for  '  proximate'  analyses.  When  analyses  are  to  be  used  as  a  basis  for 
calculating  the  heating  effect  of  the  coal  a  correction  should  be  made." 

Determination  of  Fixed  Carbon. 

"  This  is  found  by  subtracting  the  per  cent,  of  ash  from  the  per  cent, 
of  coke  as  found  above.  Sulphur,  which  passes  partly  into  the  Volatile 
Combustible  Matter  and  partly  into  the  coke,  is  not  considered  in  the 
calculation." 

Determination  of  Sulphur. 

Weigh  I  gramme  of  the  finely  ground  coal  or  coke,  and  mix  it 
thoroughly,  by  grinding  in  a  large  agate  or  porcelain  mortar,  with  10 
grammes  of  dry  sodium  carbonate  and  6  grammes  of  potassium  nitrate. 
During  the  mixing  it  is  well  to  have  the  mortar  on  a  large  sheet  of  white 
glazed  paper,  to  catch  any  particles  that  may  be  thrown  from  it.  Transfer 
the  mixture  to  a  large  platinum  crucible,  clean  the  mortar  by  grinding  a 
little  sodium  carbonate  in  it,  transfer  this  and  any  particles  that  may  be  on 
the  paper  to  the  crucible,  cover  the  latter  with  a  lid,  and  place  it  on  a 
triangle  over  an  alcohol  lamp.  Heat  the  crucible  very  carefully,  and  raise 


DETERMINATION  OF  SULPHUR.  291 

the  heat  very  slowly,  cautiously  removing  the  lid  of  the  crucible  from  time 
to  time  to  see  that  the  fusion  does  not  boil  over.  It  is  very  necessary  that 
an  alcohol  lamp  be  used  for  this  fusion,  as  the  sulphur  in  ordinary  gas  will 
certainly  vitiate  the  result.  When  the  mass  in  the  crucible  is  in  a  tranquil 
state  of  fusion,  run  it  up  on  the  sides  of  the  crucible,  cool,  treat  with  hot 
water,  and  wash  out  into  a  small  clean  beaker.  Filter  from  the  insoluble 
matter,  acidulate  the  filtrate  with  hydrochloric  acid,  and  evaporate  to 
dryness.  Redissolve  in  water  with  a  few  drops  of  hydrochloric  acid, 
filter,  dilute  the  filtrate  to  about  500  c.c.,  heat  to  boiling,  and  add  from  10 
to  20  c.c.  of  a  strong  solution  of  barium  chloride.*  Allow  the  precipitated 
barium  sulphate  to  settle,  decant  the  clear,  supernatant  fluid  through  a 
filter  or  a  felt  on  a  Gooch  crucible,  heat  the  precipitate  with  a  solution  of 
ammonium  acetate, f  transfer  it  to  the  filter,  wash  well  with  hot  water,  dry, 
ignite,  and  weigh  as  barium  sulphate,  which,  multiplied  by  .13756,  gives 
the  weight  of  sulphur.  The  time  of  the  operation  may  often  be  very  much 
shortened  by  adding  an  excess  of  ammonia  to  the  acidulated  filtrate  of  the 
aqueous  solution  of  the  fusion,  and  boiling  the  solution  while  passing 
a  rapid  current  of  carbonic  acid  gas  through  it.  This  precipitates  the 
silica,  alumina,  etc.,  and,  after  filtering  this  off,  acidulate  by  hydrochloric 
acid,  and  precipitate  the  barium  sulphate  as  above  directed. 

A  blank  determination,  using  the  same  amount  of  sodium  carbonate, 
potassium  nitrate,  and  hydrochloric  acid,  should  always  be  made  with 
every  new  lot  of  reagents,  and  the  amount  of  barium  sulphate  found 
subtracted  from  the  amount  of  barium  sulphate  in  every  analysis  before 
calculating  the  amount  of  sulphur  in  the  coal  or  coke. 

Determination  of  Sulphur.J     (Eschka's  Method.) 

"  Eschka's  method  is  recommended  for  general  use.  The  following 
directions,  which  are  given  for  the  convenience  of  those  using  this  re- 
port, are  those  of  G.  L.  Heath  §  with  slight  modifications. 

*  See  page  51.        ,.  /  f  See  page  45. 

\  From  Report  of  Com.  on  Coal  Analysis,  ante. 
$  Journal  American  Chem.  Soc.,  xx.  630. 


292  ANALYSIS   OF  COAL   AND    COKE. 

"  Mix  thoroughly  I  gramme  of  the  finely  powdered  coal  *  with  I 
gramme  of  magnesium  oxide  and  j£  gramme  of  dry  sodium  carbonate  in 
a  thin  platinum  dish  having  a  capacity  of  from  75  to  100  c.c.  A  crucible 
may  be  used,  but  a  dish  is  preferred.  The  magnesium  oxide  should  be 
light  and  porous,  not  a  compact,  heavy  variety. 

"  The  dish  is  heated  on  a  triangle  over  an  alcohol  lamp,  held  in  the 
hand  at  first.  Gas  must  not  be  used,  because  of  the  sulphur  it  contains. 
The  mixture  is  frequently  stirred  with  a  platinum  wire  and  the  heat 
raised  very  slowly,  especially  with  soft  coals.  The  flame  is  kept  in 
motion  and  barely  touching  the  dish,  at  first,  till  strong  glowing  has 
ceased,  and  is  then  increased  gradually  till,  in  fifteen  minutes,  the  bot- 
tom of  the  dish  is  at  a  low  red  heat.  When  the  carbon  is  burned,  transfer 
the  mass  to  a  beaker  and  rinse  the  dish,  using  about  50  c.c.  of  water.  Add 
15  c.c.  of  saturated  bromine-water  and  boil  for  five  minutes.  Allow  to 
settle,  decant  through  a  filter,  boil  a  second  and  third  time  with  30  c.c. 
of  water,  and  wash  till  the  filtrate  gives  only  a  slight  opalescence  with 
silver  nitrate  and  nitric  acid.  The  volume  of  the  filtrate  should  be  about 
200  c.c.  Add  1^2  c.c.  of  concentrated  hydrochloric  acid  or  a  corre- 
sponding amount  of  dilute  acid  (8  c.c.  of  an  acid  of  8  per  cent.).  Boil 
till  the  bromine  is  expelled,  and  add  to  the  hot  solution  drop  by  drop, 
especially  at  first,  and  with  constant  stirring,  10  c.c.  of  a  10  per  cent, 
solution  of  barium  chloride.  Digest  on  the  water-bath  or  over  a  low 
flame,  with  occasional  stirring  till  the  precipitate  settles  clear  quickly. 
Filter  and  wash,  using  either  a  Gooch  crucible  or  a  paper  filter.  The 
latter  may  be  ignited  moist  in  a  platinum  crucible,  using  a  low  flame  till 
the  carbon  is  burned. 

"  In  the  case  of  coals  containing  much  pyrites  or  calcium  sulphate,  the 
residue  of  magnesium  oxide  should  be  dissolved  in  hydrochloric  acid 
and  the  solution  tested  for  sulphuric  acid. 

"  If  desirable,  the  burning  of  the  coal  with  Eschka's  mixture  may  be 
carried  out  in  a  muffle,  from  twenty  to  thirty  minutes  being  required."! 

*  With  coals  high  in  moisture  a  correction  may  be  necessary  on  account  of  the  loss  of  water  in 
powdering  the  coal.     (  See  above  under  Moisture. ) 
f  Rothe,  Stahl  und  Eisen,  xii.  31  (1894). 


DETERMINATION  OF  PHOSPHORIC  ACID.  293 

In  reporting  the  results  of  a  coal  analysis  the  sulphur  should  always 
be  reported  as  a  separate  matter,  and  no  attempt  should  be  made  to 
distribute  it  between  the  Volatile  Combustible  Matter,  Fixed  Carbon,  and 
Ash.  The  reason  for  this  is  obvious  when  we  consider  the  conditions 
in  which  sulphur  exists  in  coal,  and  the  difficulty  which  attends  any 
attempt  to  determine  the  amount  existing  in  any  one  condition. 

Sulphur  is  known  to  exist  in  coal  in  three  conditions, — as  a  metallic 
sulphide,  such  as  pyrites,  as  calcium  or  barium  sulphate,  and  as  a  sul- 
phuretted hydrocarbon.  In  a  proximate  analysis  of  coal  about  one-half 
the  sulphur  in  any  pyrites  present  and  all  the  sulphur  existing  as  a  sul- 
phuretted hydrocarbon  are  probably  driven  off  with  the  Volatile  Com- 
bustible Matter.  The  rest  of  the  sulphur  from  the  pyrites  is  oxidized 
and  driven  off  during  the  burning  of  the  Fixed  Carbon  (iron  sulphate 
being  easily  decomposed  at  a  bright  red  heat)  unless  the  sulphuric  acid 
formed  is  taken  up  by  an  alkali  or  alkaline  earth. 

The  nearest  approach  we  can  make  to  a  determination  of  the  con- 
ditions in  which  the  sulphur  exists  in  any  coal  is  to  make  a  determina- 
tion of  the  total  sulphur  by  fusion,  and  a  determination  of  the  sulphuric 
acid  in  the  ash.  By  subtracting  the  sulphur  found  by  the  latter  deter- 
mination from  the  total  sulphur  the  difference  may  be  taken  to  represent 
the  amount  existing  as  sulphur  (in  the  form  of  sulphide),  and  the 
amount  found  in  the  ash  as  that  existing  as  sulphuric  anhydride  (in  the 
form  of  sulphate).  These  results  will  be  correct  if  the  coal  contains  no 
carbonates  of  the  alkalies  or  alkaline  earths. 

Determination  of  Phosphoric  Acid. 

Burn  off  10  grammes  of  the  coal  or  coke  in  a  crucible,  or,  as  in 
anthracite  coal  or  coke  this  is  a  very  tedious  operation,  burn  it  off  in  a 
large  platinum  boat  in  a  tube  in  a  current  of  oxygen.  A  boat  4  inches 
(102  mm.)  long,  and  wide  enough  to  fit  in  a  tube  ^  of  an  inch  (19  mm.) 
in  diameter,  will  hold  10  grammes  very  easily,  and  by  its  use  this  amount 
of  coke  or  anthracite  coal  may  be  burned  off  in  a  current  of  oxygen  in 
about  one  and  a  half  hours.  Treat  the  ash  with  hydrochloric  acid  to 
dissolve  any  calcium  phosphate,  filter,  and  wash  well  with  water.  Stand 


294  ANALYSIS   OF  COAL   AND    COKE. 

the  filtrate  aside,  dry,  ignite,  and  fuse  the  insoluble  matter  with  sodium 
carbonate.  Dissolve  in  water,  filter  from  the  insoluble  matter,  acidulate 
the  filtrate  with  hydrochloric  acid,  and  evaporate  to  dryness.  Redissolve  in 
water  and  a  little  hydrochloric  acid,  add  this  filtrate  to  the  hydrochloric 
acid  filtrate  from  the  first  treatment  of  the  ash,  add  a  little  ferric 
chloride  solution  and  a  slight  excess  of  ammonia.  Acidulate  with  acetic 
acid,  heat  to  boiling,  boil  for  a  few  minutes,  filter,  and  wash  the  precipitate 
once  or  twice  with  boiling  water.  Dissolve  the  precipitate  in  hydrochloric 
acid,  evaporate  nearly  to  dryness,  add  citric  acid,  magnesia-mixture,  and 
ammonia,  and  precipitate  as  directed  on  page  84.  Filter,  ignite,  and 
weigh  the  magnesium  pyrophosphate  as  there  directed.  Or,  after  dis- 
solving the  acetate  precipitate,  as  above,  in  hydrochloric  acid,  evaporate 
down,  and  precipitate  the  phosphoric  acid  by  molybdate  solution,  as 
directed  on  page  97  et  seq. 


ULTIMATE   ANALYSIS.* 

"  It  seems  to  be  unnecessary  to  give  directions  for  the  determinations 
of  carbon,  hydrogen,  and  nitrogen  here.  In  determining  carbon  and 
hydrogen,  lead  chromate  or  some  other  means  for  retaining  sulphur 
must,  of  course,  be  used.  The  amount  of  nitrogen  is  so  small  that  the 
use  of  a  copper  spiral  is  not  necessary." 

"  The  method  to  be  used  in  calculating  the  oxygen  of  the  coal  pre- 
sents, perhaps,  the  question  of  greatest  difficulty.  If  we  could  be  sure 
that  all  of  the  sulphur  is  present  in  the  form  of  pyrites,  and  that  this  is 
converted  into  ferric  oxide  in  the  ash,  the  oxygen  should  be  found  by 
subtracting  from  100  the  sum  of  carbon,  hydrogen,  nitrogen,  ash,  and  five- 
eighths  of  the  sulphur.  This  is  probably  the  safest  rule  which  can  be  given 
for  general  use,  and  especially  for  coals  high  in  sulphur.  The  operator 
should,  however,  satisfy  himself  as  to  whether  the  ash  is  practically  free 


*  From  Report  of  Com.  on    Coal  Analysis,  ante. 


ULTIMATE   ANALYSIS. 

from  sulphates,  and,  if  possible,  whether  the  sulphur  is  mainly  in  the 
form  of  pyrites.  If  necessary,  the  rule  should  be  modified,  in  particular 
cases,  accordingly." 

Heating  Effect. 

"  In  the  preliminary  report  the  recommendation  was  made  that  the 
heating  effect  be  given  on  the  basis  of  the  coal  burned  to  vapor  of 
water  .at  100°  C.  After  some  criticism  from  others  and  further  consid- 
eration, we  have  concluded  to  recommend  that  results  be  given  for  the 
coal  burned  to  liquid  water  at  the  ordinary  temperature.  The  reasons 
for  this  recommendation  are  that  this  appears  to  be  the  common  prac- 
tice in  this  country,  and  because  coals  are  burned  to  liquid  water  in  the 
bomb  calorimeter,  which  undoubtedly  furnishes  the  best  determinations 
of  heating  effect  at  present  available.  Engineers  and  others  will,  of 
course,  understand  that  the  heating  effect,  when  stated  in  this  manner, 
includes  from  3^  to  4  per  cent,  of  heat  which  can  never  be  secured  under 
the  conditions  of  practical  use. 

"  The  most  reliable  formula  for  the  calculation  of  the  heating  effect  of 
a  coal  burned  to  liquid  water  is  that  of  Dulong,  which  gives  the  calo- 
rific power  in  calories  per  kilogramme. 

"  Calorific  power  =  8080  C  -f  34,460  (H —  -  O)  -f-  2250  S. 

8 

"  For  the  calculation  of  the  oxygen,  see  the  paragraph  above  on  ulti- 
mate analysis." 

"  The  calorific  power  in  British  Thermal  Units  per  pound  may  be 
found  by  multiplying  that  in  calories  per  kilogramme  by  nine-fifths." 

"  The  theoretical  evaporative  effect  is  to  be  calculated  by  dividing  the 
number  of  calories  per  kilogramme  by  536,  or  the  number  of  British 
Thermal  Units  per  pound  by  965,  and  subtracting  from  the  result  one- 
seventh  more  than  the  amount  of  water  formed  by  burning  one  kilo- 
gramme of  the  coal.  The  addition  of  one-seventh  is  given  because  the 
liquid  water,  on  the  basis  of  which  the  heating  effect  is  given,  must  be 
considered  as  changed  from  water  at  ordinary  temperature  to  steam  at 
1 00°  C.  The  amount  to  be  subtracted  may  be  taken  as  0.55  for  most 


296  ANALYSIS   OF  COAL   AND    COKE. 

bituminous  coals.  The  result  gives  the  theoretical  number  of  kilo- 
grammes, or  pounds,  of  water  converted  into  steam  from,  and  at,  100° 
C.  by  one  kilogramme,  or  pound,  of  coal." 

"  The  rule  given,  tentatively,  in  our  preliminary  report  for  the  calcula- 
tion of  heating  effect,  from  the  amount  of  combustible  matter  present  in 
bituminous  coals,  has  been  found  to  be  of  limited  application." 


METHODS   FOR  THE  ANALYSIS 


OF 


GASES. 


THE  technical  analysis  of  gases  is  of  growing  importance,  and  a 
knowledge  of  the  methods  of  analysis  and  of  the  manipulation  involved  is 
now  generally  necessary  to  the  iron  chemist.  For  ease  of  manipulation, 
and  for  the  accuracy  of  the  results  obtained  by  its  use,  Hempel's  form 
of  apparatus  is  generally  to  be  preferred.  It  consists  essentially  of  a 
burette  for  holding  and  measuring  the  gas,  B,  Fig.  103  (the  modified 
Winkler's  gas-burette),  and  a  pipette,  G  (Fig.  106),  which  holds  the 
reagent.  By  means  of  the  level-tube  A,  filled  with  water,  the  gas  is 
forced  into  the  pipette,  where  it  is  brought  in  contact  with  the  reagent 
and  afterwards  returned  to  the  burette  and  measured.  By  the  use  of  a 
series  of  these  pipettes,  each  filled  with  a  separate  reagent,  the  various 
constituents  of  the  gas  under  examination  are  absorbed  and  their  volumes 
estimated. 


COLLECTING    SAMPLES. 

Fig.  100  shows  a  very  simple  method  for  taking  a  sample  of  gas  for 
analysis.  The  porcelain  tube  A  passes  through  the  brick-work  into  the 
flue  through  which  the  gas  is  carried.  In  the  sketch  a  portion  of  the 
porcelain  tube  is  cut  away,  to  show  the  loose  filaments  of  asbestos  with 
which  the  tube  is  filled  to  keep  dust  or  tarry  matter  from  entering  the  burette. 
This  asbestos  must  be  put  in  very  loosely,  or  it  will  pack  and  interfere 

297 


298 


ANALYSIS   OF  GASES. 


with  the  free  passage  of  the  gas.  Where  the  gas,  as  from  a  producer,  etc., 
is  constantly  examined,  it  is  very  convenient  to  have  a  valve  fitted  per- 
manently to  an  iron  pipe  screwed  or  cemented  into  the  flue,  into  which  the 
porcelain  tube  may  be  fastened  by  means  of  a  rubber  or  asbestos  *  stopper. 
A  glass  tube  of  about  j{  inch  (6  mm.)  diameter  is  fitted  into  the  outer  end 
of  the  porcelain  tube  A  (Fig.  103)  by  means  of  a  rubber  or  asbestos  stopper, 
and  this  glass  tube  is  connected  by  means  of  the  rubber  tube  C  with  the 

FIG.  103. 


opening  at  the  lower  end  of  the  burette  d.  If  the  gas  is  under  pressure  (as 
is  rarely  the  case),  it  is  only  necessary  to  open  the  stopcocks  and  allow  it 
to  pass  through  the  burette  until  the  air  is  entirely  displaced.  Usually, 
however,  it  is  necessary  to  draw  the  gas  through ;  and  the  little  india- 
rubber  pump  D  attached  to  the  capillary  tube  at  the  tipper  end  of  the 
burette  is  very  useful  for  this  purpose.  It  is  fitted  with  a  simple  valve  at 
each  end,  so  that  by  compressing  the  bulb  in  the  hand  its  contents  are  dis- 


See  page  144. 


COLLECTING   SAMPLES.  299 

charged  through  the  outer  end  while  the  pressure  closes  the  valve  at  the 
burette  end.  When  the  bulb  is  released  it  resumes  its  shape,  the  tension 
closing  the  outer  valve  and  opening  the  one  towards  the  burette,  through 
which  the  contents  of  the  latter  are  drawn  into  the  bulb.  A  bulb  of  the 
usual  size  will  empty  a  100  c.c.  burette  in  about  three  strokes.  In  taking  a 
sample  of  gas,  turn  the  three-way  stopcock  b  so  that  the  passage  is  open 
through  into  the  burette,  open  the  stopcock  a  at  the  upper  end  of  the 
burette,  and  pump  the  gas  through  slowly  for  five  or  six  minutes.  Close 
the  upper  stopcock  a,  compress  the  rubber  tube  C  between  the  thumb  and 
fingers  of  the  left  hand,  and,  holding  the  tube  with  the  other  hand,  slide 
the  left  hand  towards  the  burette.  This  will  compress  the  gas  in  the 
burette,  and  by  closing  the  stopcock  b  while  the  tube  C  is  thus  held 
the  gas  in  the  burette  will  be  under  pressure.  In  closing  b,  it  must  be 
turned  so  that  the  passage  is  open  from  d  out  through  c,  as  shown  in 
Fig.  104.  Remove  the  burette  to  the  labora- 
tory, attach  the  rubber  tube  C  of  the  level-tube 
A  (Fig.  1 06)  to  the  end  of  the  burette,  loosen 
the  pinchcock  E,  and  allow  the  water  to  run 
through  until  it  comes  out  through  the  rubber 
tube  on  the  end  of  the  stopcock.  Close  E,  and 
allow  the  burette  and  gas  to  attain  the  tem- 
perature of  the  laboratory.  Samples  of  gas 
for  analysis  may  also  be  taken  in  glass  tubes 
drawn  out  at  the  ends  and  closed  by  rubber 

tubes  and  pinchcocks  or  pieces  of  glass  rod.  When  the  sample  is  to  be 
taken  to  a  distance,  it  may  often  be  collected  in  a  metal  vessel  with 
conical  ends  and  tubes  with  well-ground  stopcocks.  Glass  vessels  of 
the  proper  shape,  holding  from  half  a  litre  to  one  litre,  and  fitted  with  glass 
stopcocks  and  capillary  tubes  made  for  this  purpose,  may  be  purchased  from 
dealers  in  chemical  glass-ware.  From  these  vessels  or  tubes  the  gas  may 
be  transferred  to  the  burette  by  attaching  to  one  outlet  a  tube  filled  with 
water  and  joined  to  the  burette,  likewise  filled  with  water,  placing  the 
other  end  of  the  vessel  in  water,  lowering  the  level-tube,  and  drawing 
the  gas  into  the  burette. 


300  A  A' A  LYSIS    OF  GASES. 

REAGENTS    FOR   THE    PIPETTES. 

Blast-furnace  gas,  producer  gas,  and,  in  general,  gases  made  by  draw- 
ing or  forcing  atmospheric  air  through  coal  or  coke,  contain  varying 
amounts  of  carbon  dioxide  (CO2),  oxygen  (O),  carbon  monoxide  (CO), 
hydrogen  (H),  methane,  or  marsh  gas  (CH4),  and  nitrogen  (N).  The  best 
absorbents  are  caustic  potash  for  carbon  dioxide,  pyrogallol  for  oxygen,  and 
cuprous  chloride  in  hydrochloric  acid  for  carbon  monoxide.  Hydrogen  is 
determined  by  ignition  with  excess  of  oxygen  over  palladium  sponge,  and 
marsh  gas  by  ignition  in  a  tube  filled  with  cupric  oxide.  The  pipettes 
required,  therefore,  are  a  simple  pipette  (G,  Fig.  106)  filled  with  caustic 
potash  (1.27  sp.  gr.)  for  absorbing  carbonic  acid,  which  is  readily  filled  by 
placing  in  the  large  tube  of  the  pipette  a  small  glass  tube,  which  extends 
down  to  the  bottom  of  the  bulb  and  is  connected  outside  with  a  small  glass 
funnel  by  means  of  a  piece  of  rubber  tubing.  Pour  the  caustic  potash  in 
through  the  funnel  until  the  large  bulb  of  the  pipette  and  the  tube  connect- 
ing the  two  bulbs  are  filled  with  the  liquid.  Draw  the  liquid  into  the 
capillary  tube  until  it  reaches  to  within  a  very  short  distance  of  the  rubber 
tube  on  the  end  of  the  capillary,  and  close  the  rubber  tube  with  a  piece  of 
glass  tubing  or  a  pinchcock,  as  shown  in  the  sketch  of  the  composite 
pipette  (Fig.  105). 

A  composite  pipette  containing  pyrogallol  for  absorbing  oxygen 
is  filled  as  follows.  Dissolve  30  grammes  of  pyrogallic  acid  in  75  c.c. 

of  water,  attach  a  funnel  to  the  capillary  tube 
of  the  pipette  by  a  piece  of  rubber  tubing,  and 
fill  it  with  the  solution.  Attach  a  piece  of 
rubber  tubing  to  the  other  tube  of  the  pipette, 
and  by  gentle  suction  exhaust  the  air;  this  will 
cause  the  liquid  to  run  rapidly  through  the  capil- 
lary tube  into  the  pipette.  Keep  the  funnel  full 
until  the  liquid  which  is  drawn  through  the 

large  bulb  into  the  second  bulb  fills  the  latter  to  an  inconvenient  extent, 
then  stop  the  suction,  and  very  carefully  blow  the  liquid  back  into  the 
large  bulb.  Fill  the  funnel  again,  and  exhaust  the  air  gently  as  before. 


REAGENTS  FOR    THE   PIPETTES.  30 1 

Repeat  this  until  all  the  solution  of  pyrogallic  acid  has  been  drawn  in, 
and  then  with  the  same  precautions  draw  in  a  solution  of  caustic  potash 
(1.27  sp.  gr.)  until  the  large  bulb  and  the  tube  connecting  the  large  bulb 
and  the  second  bulb  are  filled  with  the  liquid,  which  is  now  an  alkaline 
solution  of  potassium  pyrogallate.  Close  the  capillary  tube  as  directed 
for  the  caustic  potash  pipette  (page  300).  Insert  the  small  tube  and 
funnel  in  the  large  tube  of  the  composite  pipette,  as  directed  for  filling 
the  simple  pipette,  and  pour  a  little  water  into  the  last  bulb  of  the 
composite  pipette.  The  amount  of  water  poured  in  should  not  be 
sufficient  to  fill  the  third  bulb,  for  the  pyrogallol  rapidly  absorbs  the 
oxygen  of  the  air  in  the  second  bulb,  and  this  contraction  causes  the 
water  poured  into  the  last  bulb  to  rise  in  the  third  bulb.  Therefore 
the  amount  of  water  should  be  small  enough  to  permit  small  bubbles  of 
air  to  pass  through  to  supply  the  contraction  in  the  second  bulb,  and 
large  enough  to  avoid  emptying  the  third  bulb  when  during  an  analysis 
the  gas  is  forced  through  the  capillary  into  the  large  bulb  of  the  pipette. 
The  amount  of  potassium  pyrogallate  from  30  grammes  of  pyrogallic 
acid  is  sufficient  to  absorb  nearly  1500  c.c.  of  pure  oxygen,  so  that 
a  composite  pipette  filled  in  this  way,  and  securely  sealed  by  the 
water  in  the  third  and  fourth  buibs,  will  last  for  a  great  number  of 
analyses. 

Another  composite  pipette  for  absorbing  carbon  monoxide  is  filled, 
as  above  described,  with  a  saturated  solution  of  cuprous  chloride  in  hydro- 
chloric acid  (i.i  sp.  gr.)  and  sealed  with  water.  Each  pipette  should  be 
distinctly  labelled  with  the  name  of  the  reagent,  so  that  no  mistake  can 
be  made  in  using  them. 

It  is  worthy  of  note  that  the  absorption  of  carbon  monoxide  by 
cuprous  chloride  is  purely  mechanical,  and  is  never  absolutely  perfect,  so 
that  a  small  amount  of  carbon  monoxide  invariably  remains  in  the  gas 
after  treatment  in  the  cuprous  chloride  pipette.  Moreover,  whenever  a 
gas  absolutely  free  from  carbon  monoxide  is  treated  in  a  cuprous 
chloride  pipette  (which  has  previously  been  used  to  absorb  carbon  mon- 
oxide) and  returned  to  the  burette,  it  will  be  'found  to  have  increased 
in  volume,  and  subsequent  combustion  in  a  palladium  tube  will  yield  an 


302  ANALYSIS   OF  GASES. 

amount  of  carbonic  acid  corresponding  to  this  increase  counted  as  carbon 
monoxide.  If  this  fact  is  overlooked,  the  carbon  monoxide  left  in  the 
gas  will  be  counted  as  methane  if  a  determination  of  this  gas  is  made 
in  the  usual  course  of  the  analysis. 

A  composite  pipette  filled  with  bromine-water  to  absorb  ethylene 
(C2HJ  is  sometimes  used,  as  this  gas  has  been  found  in  the  gases  from 
blast-furnaces  and  producers  using  bituminous  coal.  But  the  amount  of 
ethylene  is  very  small,  and  a  separate  determination  is  rarely  made,  any 
small  amount  being  absorbed  and  determined  as  carbon  monoxide. 


ANALYSIS    OF   THE    SAMPLE. 

The  burette  containing  the  gas,  with  the  level-tube  filled  with  water 
attached,  as  mentioned  on  page  299,  having  attained  the  temperature  of 
the  laboratory,  raise  the  level-tube  and  open  the  three-way  stopcock  so 
that  the  passage  is  open  for  the  water  to  enter  the  burette.  If  the  gas  is 
shown  to  be  under  a  slight  pressure,  by  raising  or  lowering  the  burette 
bring  the  water  just  to  the  stopcock  (if  the  burette  is  graduated  to  read 
100  c.c.  from  stopcock  to  stopcock,  otherwise  bring  the  water  to  the 
o  mark),  and  close  the  stopcock.  Then  open  the  upper  stopcock  for  an 
instant  to  allow  the  gas  to  assume  the  pressure  of  the  atmosphere. 
Now  open  the  three-way  stopcock  to  allow  the  water  to  enter  the  burette, 
hold  the  level-tube  so  that  the  water  in  the  tube  and  that  in  the  burette 
are  at  the  same  level,  and  observe  the  reading  of  the  burette.  It  is  a 
very  simple  matter  in  this  way  to  get  exactly  100  c.c.  of  gas,  which  very 
materially  simplifies  the  calculations.  Connect  the  burette  with  the  pipette 
containing  caustic  potash  by  means  of  the  capillary  connecting-tube,  as 
shown  in  Fig.  106.  Some  little  skill  is  necessary  in  making  this  con- 
nection ;  the  best  way  to  arrange  it  is  as  follows.  Attach  one  end  of 
the  capillary  connecting-tube  to  the  top  of  the  burette  by  a  piece  of  rubber 
tubing,  wiring  it  if  necessary,  then  compress  between  the  thumb  and 
forefinger  of  one  hand  the  rubber  tube  on  the  capillary  of  the  pipette  for 
its  entire  length  above  the  pinchcock  (as  shown  in  Fig.  105),  then  care- 
fully introduce  the  end  of  the  capillary  connecting-tube  into  the  end  of 


ANALYSIS    OF   THE   SAMPLE. 


303 


FIG.  106. 


the  rubber  tube  and  release  the  rubber  tube.  If  this  is  carefully  done 
the  walls  of  the  rubber  tube  between  the  pinchcock  and  the  end  of  the 
capillary  will  remain  in  contact,  showing  that  no  air  has  been  admitted. 
Force  the  end  of  the  capillary  tube  down  to  the  pinchcock,  and  open  the 
latter,  allowing  it  to  remain  over  the 
capillary  as  shown  in  Fig.  107.  The 
apparatus  will  now  be  in  the  position 
shown  in  Fig.  106.  Open  the  upper 
stopcock  of  the  burette,  and  then  turn 
the  three-way  stopcock  D  carefully  to 
admit  the  water  from  the  level-tube  into 
the  burette.  As  the  water  enters  the 
burette  the  gas  is  forced  over  into  the 
pipette  G.  Allow  the  water  to  completely 
fill  the  burette  B  and  to  enter  the  capil- 
lary tube  F  and  fill  it  as  far  as  the 
rubber  connection  between  it  and  the 
capillary  tube  of  the  pipette  G.  Close 
the  upper  stopcock  of  the  burette,  place 
the  pinchcock  on  the  rubber  tube  between 
the  capillary  connecting-tube  and  the 
pipette,  and  remove  the  capillary  con- 
necting-tube F  from  the  rubber  tube  of 
the  pipette,  leaving  it  attached  to  the 
burette.  Take  the  pipette  from  the  stand 
and  shake  it,  to  promote  the  absorption 
of  the  carbonic  acid,  which  will  require 
only  a  minute  or  two.  Replace  the  pi- 
pette, attach  the  capillary  connecting-tube 
F  as  before,  remove  the  pinchcock,  place  the  level-tube  A  on  the  floor, 
open  the  upper  stopcock  of  the  burette,  and  allow  the  water  to  run  from 
the  burette  B  into  the  level-tube  A,  drawing  the  gas  from  the  pipette  G 
into  the  burette  B.  When  the  caustic  potash  solution  has  run  back  so 
as  to  fill  the  large  bulb  and  the  capillary  of  the  pipette  almost  to  the 


304  ANALYSIS    OF  GASES. 

rubber  connection,  quickly  close  the  upper  stopcock  of  the  burette  B, 
replace  the  pinchcock  on  the  rubber  tube  of  the  pipette  G,  detach  the 
capillary  connecting-tube  F  from  the  pipette,  hold  the  level-tube  A  and 
the  burette  B  together  to  get  the  water  on  an  exact  level,  and  take  the 
reading  of  the  burette.  The  difference  between  this  reading  and  the 
original  reading  will  be  the  number  of  c.c.  of  carbonic  acid  absorbed; 
and  if  the  original  reading  was  ioo  c.c.,  each  c.c.  absorbed  will  be  one  per 
cent,  of  carbonic  acid  in  the  gas.  If  any  other  volume  of  gas  was 
originally  used,  divide  the  number  of  c.c.  absorbed  by  the  number 
originally  used,  multiply  this  by  ioo,  and  the  result  is  the  percentage  of 
carbonic  acid  in  the  gas. 

If  ethylene  is  to  be  determined,  pass  the  gas  into  the  bromine-water 
pipette,  back  into  the  burette,  then  into  the  caustic  potash  pipette  to 
absorb  any  bromine  fumes,  finally  back  into  the  burette,  and  take  the 
reading  as  before.  The  contraction  is  ethylene. 

Now  pass  the  gas  into  the  pyrogallol  pipette,  shake  the  latter  gently 
for  four  or  five  minutes  to  promote  the  absorption  of  the  oxygen,  return 
the  gas  to  the  burette,  and  note  the  reading.  The  contraction  from  the 
last  reading  is  oxygen. 

Pass  the  gas  in  the  same  manner  into  the  cuprous  chloride  pipette, 
detach  and  shake  the  latter  gently  at  short  intervals  for  five  or  six  minutes 
to  promote  the  absorption  of  the  carbon  monoxide,  return  the  gas  to  the 
burette,  and  take  the  reading.  The  contraction  from  the  last  reading  is 
the  carbon  monoxide  absorbed  by  cuprous  chloride.  To  determine  the 
remaining  carbon  monoxide  and  the  hydrogen,  the  gas  is  mixed  with 
oxygen  and  burned  over  spongy  palladium.  Fig.  107  shows  the  arrange- 
ment of  the  apparatus.  A  is  the  palladium  tube,  B  the  burette,  C  a 
pipette  filled  with  water,  D  a  small  gas-burner  for  heating  the  palladium 
tube,  and  E  the  gas-pipe  attached  to  the  wood-work  of  the  pipette  and 
connected  by  a  rubber  tube  with  a  supply  of  gas.  Instead  of  a  gas-burner 
for  heating  the  palladium  tube  a  small  brass  spirit-lamp  may  be  used, 
which  is  fastened  to  the  pipette-stand  by  a  clamp  in  such  a  position  as 
to  bring  the  flame  under  the  palladium  tube.  With  any  ordinary  furnace 
or  producer  gas  which  contains  50  per  cent,  and  upwards  of  nitrogen,  the 


DETERMINATION  OF  HYDROGEN. 


305 


FIG.  107. 


best  plan  is  to  attach  an  oxygen-cylinder  to  the  top  of  the  burette,  using 
a  capillary-tube  and  rubber  connections,  and  fill  the  latter  with  oxygen 
gas.  With  water-gas,  or  when  a  supply  of  oxygen  is  not  available,  it  is 
necessary  to  transfer  a  portion  of  the  unabsorbed 
gas  in  the  burette  to  another  burette,  and  then 
to  admit  air  to  the  first  burette  until  it  is  nearly 
filled.  Of  course  it  makes  the  calculation  a 
little  more  complicated  to  change  the  volume 
of  the  gas  in  this  way  during  the  progress  of 
an  analysis,  but  in  the  case  of  nearly  pure  water- 
gas  the  use  of  oxygen  alone  would  probably  lead 
to  an  explosion,  while  with  other  gases,  in  the 

absence  of  a  supply  of  oxygen,  simply  filling  the  burette  with  air  without 
letting  out  any  of  the  gas  might  not  admit  enough  oxygen  to  burn  the 
hydrogen.  After  transferring  a  portion  of  the  unabsorbed  gas,  read  the 
burette  carefully  to  get  the  volume  of  gas  taken  for  combustion,  and  then 
divide  the  volume  of  gas  taken  for  combustion  by  the  total  volume  unab- 
sorbed, and  multiply  by  the  amount  originally  taken  for  analysis ;  the  re- 
sult is  the  number  of  c.c.  of  the  original  gas,  to  which  the  amount  taken 
for  combustion  corresponds. 

After  admitting  air  to  the  burette,  which  is  done  by  standing  the 
level-tube  on  the  floor  while  the  burette  is  on  the  table,  opening  the 
three-way  stopcock  so  that  the  water  may  run  into  the  level-tube,  and 
opening  the  upper  stopcock  of  the  burette  until  the  proper  amount  of  air 
has  been  drawn  in,  take  the  reading  of  the  burette  with  care.  Connect 
the  apparatus  as  shown  in  Fig.  107,  light  the  gas-jet  D,  open  the  upper 
stopcock  of  the  burette  B,  and  by  opening  very  carefully  the  three-way 
stopcock  of  the  burette  cause  the  gas  to  pass  very  slowly  into  the  pipette 
C.  The  palladium  tube  should  not  be  heated  to  redness,  but  to  a 
temperature  just  below  a  dark-red  heat.  It  is  very  necessary  to  avoid 
carrying  over  any  water  into  the  hot  palladium  tube,  as  it  would  be  certain 
to  crack  it,  and  for  this  reason  it  is  well  to  see  that  the  capillary  tube 
above  the  stopcock  of  the  burette  and  both  capillary  ends  of  the  palladium 
tube  are  dry  before  making  the  connections.  Any  little  moisture  may  be 


20 


306  ANALYSIS    OF   GASES. 

removed  by  means  of  a  very  fine  wire  wrapped  with  thread.  As  the 
water  from  the  combustion  of  the  hydrogen  in  the  palladium  is  liable  to 
condense  in  the  end  of  the  tube  near  the  pipette,  it  is  always  well  to  warm 
this  gently  with  the  flame  of  a  small  spirit-lamp  or  a  piece  of  glowing 
charcoal,  so  as  to  drive  all  the  moisture  into  the  pipette,  and  thus  prevent 
its  being  carried  into  the  hot  part  of  the  palladium  tube  when  the  gas  is 
returned  into  the  burette.  When  the  water  has  risen  in  the  burette  just 
above  the  upper  stopcock,  lower  the  level-tube  and  draw  the  gas  back 
very  slowly  into  the  burette.  When  the  water  in  the  pipette  has  risen  to 
the  usual  position  in  the  capillary,  replace  the  pinchcock  on  the  rubber 
connection  between  the  palladium  tube  and  the  capillary  tube  of  the 
pipette,  extinguish  the  light  under  the  palladium  tube,  and,  when  the  latter 
is  cold,  close  the  upper  stopcock  of  the  burette,  detach  the  apparatus, 
open  the  three-way  stopcock  fully,  and  take  the  reading  of  the  burette. 
Now,  if  there  were  no  carbon  monoxide  present  in  the  gas  before  the 
combustion,  the  contraction  would  be  due  to  the  condensation  of  the  water 
formed  by  the  combustion  of  the  hydrogen,  and,  as  2  volumes  of  hydrogen 
unite  with  I  volume  of  oxygen  to  form  water,  J^  of  the  contraction  would 
be  hydrogen.  In  the  presence  of  carbon  monoxide,  however,  there  is  an 
additional  contraction  beyond  that  caused  by  the  formation  of  water,  due 
to  the  fact  that  2  volumes  of  carbon  monoxide  uniting  with  i  volume 
of  oxygen  form  2  volumes  of  carbonic  acid.  By  absorbing  the  carbonic 
acid  in  the  caustic  potash  pipette,  and  then  reading  the  burette,  the  second 
contraction  is  the  volume  of  the  carbonic  acid,  which  is  the  volume  of  the 
carbon  monoxide.  The  first  contraction,  then,  is  f  of  the  hydrogen  -j-  ]/% 
the  carbon  monoxide,  and  the  second  contraction  being  the  volume  of  the 
carbon  monoxide,  it  may  be  stated  thus  : 

first  contraction  =  f  hydrogen  -j-  \  second  contraction, 
or  f  hydrogen  =  first  contraction  —  \  second  contraction  ; 

multiplying  by  f, 

Hydrogen  =  f  first  contraction  —  \  second  contraction. 
Divide  the  number  of  c.c.  of  hydrogen  and  carbon  monoxide  respectively 
as  found  above  by  the  number  of  c.c.  of  the  original  gas  to  which  the 
amount  taken  for  combustion  is  equivalent,  multiply  by  100,  and  the  result 


DETERMINATION  OF  METHANE. 


307 


is  the  percentage  of  hydrogen  and  carbon  monoxide.  This  percentage 
of  carbon  monoxide  is  to  be  added  to  the  percentage  found  by  absorption 
in  cuprous  chloride,  and  the  result  is  the  total  carbon  monoxide. 

There  remain  now  in  the  burette  only  nitrogen  and  methane.  The 
latter  can  be  properly  burned  only  at  a  red  heat  in  contact  with  copper 
oxide,  forming  water  and  carbonic  acid.  By  absorbing  the  carbonic  acid 
in  a  solution  of  barium  hydroxide,  standardized  by  a  normal  solution  of 
oxalic  acid,  and  then  titrating  the  barium  hydroxide,  the  volume  of 
methane  is  at  once  indicated.  As  the  normal  solution  of  oxalic  acid 
indicates  the  volume  of  methane  at  760  mm.  of  barometric  pressure  and 
o°  C.  of  temperature,  the  thermometer  and  barometer  must  be  noted,  and 
the  correction  made  according  to  the  table  (Table  V.). 

FIG.  108. 


Dissolve  5.6314  grammes  of  crystallized  oxalic  acid  in  I  litre  of  water, 
i  c.c.  of  this  solution  indicates  I  c.c.  carbonic  acid,  or  I  c.c.  methane, 
at  760  mm.  barometric  pressure  and  o°  C.  Dissolve  14.0835  grammes  of 
crystallized  barium  hydroxide  in  I  litre  of  water.  I  c.c.  of  this  solution  is 
equal  to  about  I  c.c.  of  the  oxalic  acid  solution. 


308  '  ANAL  YSIS    OF   GASES. 

The  apparatus  for  the  determination  is  shown  in  Fig.  108.  It  consists 
of  a  porcelain  tube,  EE,  in  the  combustion-furnace  F ;  the  porcelain  tube 
is  nearly  filled  with  coarse  copper  oxide  between  loose  plugs  of  asbestos, 
or  with  a  roll  of  oxidized  copper  wire  (see  page  142).  The  forward  end 
is  connected  with  two  absorption-bottles,  G,  G,  containing  barium  hydroxide 
solution.  These  bottles  are  of  such  a  size  that  25  c.c.  will  fill  them,  so  that 
the  gas  in  bubbling  through  forces  a  little  of  the  solution  up  into  the  bulb- 
tube,  thus  prolonging  the  contact.  If  they  are  a  little  too  large,  the 
solution  of  barium  hydroxide  may  be  diluted,  after  it  is  measured  in  from 
the  pipette,  with  a  little  distilled  water  to  bring  it  to  the  proper  volume. 
A  is  a  cylinder  containing  oxygen  under  pressure,  or,  if  this  is  not  available, 
a  couple  of  bottles  for  forcing  air  through  the  apparatus  may  be  sub- 
stituted (such  as  those  shown  in  Fig.  57,  page  131).  The  cylinder  and 
the  burette  B  are  connected,  as  shown  in  the  sketch  (Fig.  108),  by  means 
of  capillary  tubes  with  the  bottle  C,  containing  caustic  potash  (1.27  sp.  gr.). 
The  bottle  C  is  connected  with  the  bottle  D,  containing  sulphuric  acid, 
and  from  D  a  capillary  tube  passes  to  the  rubber  stopper  in  the  end  of 
the  porcelain  tube  EE.  Start  a  current  of  oxygen  or  air  through 
the  apparatus  (before  attaching  the  absorption-bottles  G,  G),  light  the 
burners  of  the  furnace,  and  raise  the  temperature  gradually  until  the  tube 
is  red  hot.  Continue  the  passage  of  the  oxygen  until  a  bottle  containing 
a  solution  of  barium  hydroxide  attached  to  the  end  of  the  tube  shows 
that  no  carbonic  acid  is  given  off.  Measure  out  25  c.c.  of  the  barium 
hydroxide  solution  into  each  of  the  bottles  G,  G,  and  attach  them  as 
shown  in  Fig.  108,  open  the  upper  stopcock  of  the  burette  B,  and  by 
means  of  the  three-way  stopcock  let  water  into  the  burette  from  the  level- 
tube,  so  that  the  gas  from  the  burette  is  made  to  bubble  very  slowly  into 
the  bottle  C.  About  three  or  four  bubbles  should  pass  into  C  from  the 
oxygen  cylinder  to  one  from  the  burette.  When  the  water  completely 
fills  the  burette  and  the  capillary  tube  in  C,  close  the  upper  stopcock 
of  the  burette,  and  continue  the  passage  of  the  oxygen  from  A  until  it  is 
certain  that  all  the  gas  has  been  carried  through  the  porcelain  tube  and 
the  absorption-bottles.  In  the  mean  time  measure  out  25  or  50  c.c.  of  the 
barium  hydroxide  solution  into  a  porcelain  dish,  dilute  with  water,  add  a 


.   DETERMINATION  OF  NITROGEN.  309 

drop  of  phenolphthalein  solution  (made  by  dissolving  phenolphthalein  in 
alcohol),  and  from  a  burette  run  in  the  standard  solution  of  oxalic  acid 
until  the  pink  color  of  the  solution  just  vanishes.  This  will  give  the  value 
of  the  barium  hydroxide  solution  in  terms  of  the  normal  oxalic  acid 
solution.  When  the  combustion  is  finished,  detach  the  absorption-bottles, 
wash  their  contents  into  the  dish,  add  a  drop  of  phenolphthalein  solution, 
and  titrate  with  the  oxalic  acid  solution.  The  difference  between  the  value 
of  50  c.c.  barium  hydroxide  solution  and  that  of  the  50  c.c.  from  the 
absorption-bottles,  in  terms  of  the  oxalic  acid  solution,  is  the  number  of 
c.c.  of  methane  in  the  gas  burned  at  760  mm.  barometric  pressure  and  o°  C. 
Divide  this  by  the  number  of  c.c.  burned,  reduced  to  760  mm.  pressure  and 
o°  C.,  multiply  by  100,  and  the  result  is  the  volume  per  cent,  of  methane. 
Add  together  the  percentages  obtained  of  carbonic  acid  (ethylene,  C2H4), 
oxygen,  carbon  monoxide,  hydrogen,  and  methane,  subtract  the  sum  from 
100,  and  the  remainder  is  the  percentage  of  nitrogen  by  difference. 
An  example  will  illustrate  the  method  of  analysis,  thus : 


EXAMPLE    OF   ANALYSIS. 

Siemens'  Producer  Gas. 

Volume  of  gas  employed,  99.7  c.c. 

KHO  pipette   ......    93.5  c.c.         Contraction,    6.2  c.c.  CO2  =r      6.21 

Pyrogallol  pipette    ....    93.3     "  "  0.2   "  O  •=.      0.20 

CuCl  "         ....    74.0     "  "  19.3    "    =  19.36  %  CO 

Transferred  a  portion.  From  palladium  combustion         1.42"   CO  (total)  =    20.78 

Remaining  in  pipette  .    .    .    46.8     "  H  =    11.23 

T46.8 


T46.8  n 

=  of  original  gas  to  .    .    .      63.24  L~74~X"'7J 

Admitted  air  to    .....    98.4     "  N  =    58.44 


CH* 


Burned  over  palladium  .  .  87.3  " 
First  contraction  .....  1  1.  1  " 
KHO  pipette  ......  86.4  " 

r  °-9         ~\ 

Second  contraction  .    ...      0.9     "    =  CO2  =  CO    g—  —  x  100    =  1.42  %  CO. 

H=2^  rn.i]  —  #[o.9]  =  7.i  c.c.  [5^  X  100]  =  11.23^  H. 

Burned  residue  over  oxide  of  copper  and  absorbed  CO2  in  caustic  baryta  solution. 

Thermometer  17°  C.  Barometer  745  mm.  745-°  —  14.4=  730.6 

7  .0086702  X  ioo     =.86702 
3  .0037158  X     10     =.037158 
o  X       i     =.000000 

6  .0074316  x      o.i  =  .00074316 
.90492116 
63.24  c.c.  X  .90492116  =  57.23  c.c.  at  760  mm.  and  o°  C. 

50  c.c.  caustic  baryta  solution  =  48.3  c.c.  oxalic  acid 
After  combustion  50  c.c.        "  "       =  46.5  "         "         " 

Therefore  CH4  in  gas  burned  r=    1.8  " 

1.8 
and  ^-^  X  100  =  3.14  %  CH4. 

310 


TABLES. 


TABLE    I. 

Atomic  Weights  of  the  Elements  used  in  this  Volume. 


Name. 

Symbol. 

At.  Wt. 

Name. 

Symbol. 

At.  Wt. 

Al 

27  O7 

Manganese    ....... 

Mn 

re  oo 

Antimony  . 

Sb 

1  2O.OO 

Mo 

06.00 

Arsenic           .        

As 

7C..OO 

Nickel    

Ni 

^8  70 

Barium 

Ba 

117  OO 

Nitrogen         

N 

14  O7 

Bromine 

Br 

7Q  Q$ 

Oxygen                   .    .        . 

o 

16  oo 

Calcium  .        

Ca 

AO.O8 

Phosphorus    

p 

-JQ  Q7 

Carbon 

c 

12  OO 

Platinum            ' 

Pt 

1  04  87 

Chlorine     

Cl 

•2C.AC 

Potassium      

K 

-  T.Q.II 

Chromium  .            ...        . 

Cr 

C.2  14 

Silicon    

Si 

28  4O 

Cobalt 

Co 

CQ  oo 

Sodium                       .... 

Na 

21  O^ 

Copper 

Cu 

67  40 

s 

72  06 

Hydrogen 

H 

I  007 

Tin                 

Sn 

HO  OO 

Iodine    

I 

126  85 

Ti 

48.OO 

Iron        .    .    . 

Fe 

c,6  oo 

Tungsten            

W 

184  oo 

Lead                                   , 

Pb 

206  QC, 

Vanadium                  .            . 

v 

CT   07 

Magnesium    

Mg 

24  2Q 

Zinc        

Zn 

6c,  27 

3I2 


THE   CHEMICAL   ANALYSIS   OF  IRON. 


TABLE    II. 

Table  of  Factors. 


Found. 


Required. 


Factor. 


Log. 


A1PO4 Al 

A12O3 Al 

Sb204 Sb 

Sb2S3 Sb 

Mg2(NH4)2As2O8  +  H2O As 

Mg2As207 As 

As2S3 As 

As FeAs2 

BaSO4 S 

SO3 
CaS04 CaO 

CaC03 

CaO CaC03 

CO2 C 

Cr203 Cr 

CoS04 Co 

CoO 

Co CoO 

CoO Co 

Cu CuO 

Cu2S 

CuO Cu 

CuaS Cu 

Fe203 Fe 

Fe Fe3O4 

FeO 
PbSO4 Pb 

PbO 

PbS 


0.22181 

0.53005 
0.78947 
0.71390 
0.39400 
0.48297 
0.60931 
1-37333 
O.I3756 
0.34352 
0.41193 

0.73513 
1.78459 
0.27273 
0.68479 
0.38050 
0.48370 
1.27119 
0.78667 
1.25240 
1.25284 
0.79849 
0.79818 
0.70000 

1-38095 
1.28571 
0.68298 
0.73578 
0.78879 


9.3459811-10 
9.7243168-10 


9-5954962-IO 
9.6839202-10 
9.7848383-10 

0-1377749 

9.1384922-10 

9-535952o-io 

9.6148234-10 

9.8663641-10 

0-2515385 

9.4357329-iG 

9.8355574-io 

9-5803547-10 

9.6845761-10 

0.1042105 

9.8957926-10 

0.0977431 

0.0978956 

9.9022695-10 

9.9021008-10 

9.8450980-10 

0.1401779 

0.1091430 

9.8344080-10 

9.8667480-10 

9.8969614-10 


TABLES. 

TABLE    II. — Continued. 


313 


Found. 


Required. 


Factor. 


Log. 


Mg2P207 P 

PA 

MgO 

MgC03 
Mn3O4 Mn 

MnO 
Mn2P2O7 Mn 

MnO 
MnS Mn 

MnO 
(NH4)3iiMo03P04 P 

PA 

NiO Ni 

Ni2S Ni 

K2PtCl6  . KC1 

K20 

KC1 K2C03 

NaCl Na2O 

Na2CO3 

SiO2 Si 

S FeS2 

SnO2 , Sn 

Ti02 Ti 

V205 V 

W03 W 

ZnO  Zn 


0.27836 
0.63788 
0.36212 
0.75760 
0.72052 
0.93013 
0.38741 
0.50011 
0-63I75 
0-81553 
0.01630 

0.03735 
0.78581 
0.78549 
0.30696 

0.19395 
0.92690 

0.53077 
0.90684 
0.47020 
1.87336 
0.78808 
0.60000 
0.56222 
0.79310 
0.80313 


9.4446068-10 

9.8047390-10 

9.5588525-10 

9.8794400-10 

9.8576460-10 

9.9685437-10 

9.5881708-10 

9.6990655-10 

9.8005453-10 

9.9114399-10 

8.2121876-10 

8.5722906-10 

9.8953176-10 

9.8951407-10 

9.4870818-10 

9.2876898-10 

9.9670329-10 

9.7249064-10 

9-9575307-IO 

9.6722826-10 

0.2726212 

9.8965703-10 

97781513-10 

9.7499063-10 

9.8993279-10 

9.9047858-10 


3H 


THE   CHEMICAL   ANAL  YSIS   OF  IRON. 


TABLE    III. 

Percentages  of  P  and  P2O5  for   each  Milligramme  of  Mg2P2O7  when   10 
Grammes  of  the  Sample  are  used. 


Wt.of 
Mg2P207. 

I 

P. 

P206. 

Wt.of 
Mg2P207. 

P. 

PS05. 

Wt.of 
Mg,P207. 

p. 

PA- 

Wt  of 
Mg2P207. 

P. 

P205. 

0.003 

0.006 

26 

0.073 

0.166 

51 

0.142 

0.326 

76 

0.212 

0.486 

2 

0.005 

0.013 

27 

0.075 

0.173 

52 

0.145 

0.332 

77 

0.215 

0.492 

3 

O.OOS 

0.019 

28 

0.078 

0.179 

53 

0.148 

0-339 

78 

0.218 

0.499 

4 

O.OII 

0.026 

29 

0.08  1 

0.185 

54 

0.151 

0-345 

79 

0.221 

0.505 

5 
6 

O.OI4 
O.OI7 

0.032 
0.038 

30 
31 

0.084 
0.086 

0.192 
O.I98 

55 
56 

0.154 
0.156 

0-352 
0.358 

80 
81 

O.223 
0.226 

0.512 
0.518 

7 

0.019 

0.045 

32 

0.089 

O.2O4 

57 

0.159 

0.364 

82 

O.229 

0.524 

8 

0.022 

0.051 

33 

0.092 

0.21  1 

58 

0.162 

0.371 

83 

0.232 

0.531 

9 

O.O25 

0.057 

34 

0.095 

O.2I7 

59 

0.165 

o-377 

84 

0.235 

°-537 

10 

O.O28 

0.064 

35 

0.098 

O.224 

60 

0.167 

0.384 

85 

0.237 

0-544 

ii 

0.031 

0.070 

36 

O.IOI 

0.230 

61 

0.170 

0.390 

86 

0.240 

o-55o 

12 

°-°33 

0.077 

37 

0.103 

0.237 

62 

0.173 

0.396 

87 

0.243 

0-556 

13 

0.036 

0.083 

38 

O.I  06 

0.243 

63 

0.176 

0.403 

88 

0.246 

0-563 

14 

0.039 

0.089 

39 

0.109 

0.249 

64 

0.179 

0.409 

89 

0.248 

0.569 

15 

0.042 

0.096 

40 

O.II2 

0.256 

65 

0.181 

0.416 

90 

0.251 

0.576 

16 

0.045 

0.102 

4i 

O.II4 

O.262 

66 

0.184 

0.422 

9i 

0.254 

0.582 

17 

0.047 

0.108 

42 

O.II7 

0.269 

67 

0.187 

0.428 

92 

0.257 

0.588 

18 

0.050 

O.II5 

43 

O.I  2O 

0.275 

68 

0.190 

0-434 

93 

0.259 

0-595 

19 

0-053 

O.I2I 

44 

0.123 

0.281 

69 

0.193 

0.441 

94 

O.262 

0.601 

20 

0.056 

0.128 

45 

0.126 

0.287 

70 

0.195 

0.448 

95 

0.265      0.607 

21 

0.059 

0.134 

46 

0.128 

0.294 

7i 

0.198 

0-454 

96 

0.268  i 

0.614 

22 

0.06  1 

O.I4I 

47 

0.131 

0.300 

72 

O.2OI 

0.460 

97 

0.271 

0.620 

23 

0.064 

0.147 

48 

0.134 

0.307 

73 

0.204 

0.467 

98 

0.274 

0.627 

24 

0.067 

0.153 

49 

0.137 

0.313 

74 

0.207 

0-473 

99 

0.276 

0.633 

25 

0.070 

O.I59 

50 

0.139 

0.310 

75 

0.209 

0-479  I 

100 

0.278 

0.638 

O 
o 

q 

i 


o 
O 

I 


W  43 

J  § 

W  H 

<  a 

H  a 


h 

i 


§ 
i 

<! 
^ 

§ 


TABLES.                                                                3I- 

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THE  CHEMICAL  ANALYSIS   OF  IRON. 


TABLE   V. 

Table  for  Reducing-  Volumes  of  Gases  to  the  Normal  State. 

BY   PROFESSOR   DR.    LEO   LIEBERMANN. 
(From  Winkler's  "Technical  Gas  Analysis.") 

Instructions  for   Use. 

Suppose  the  volume  of  a  gas  to  have  been  found  =26.2  c.c.  at  742  mm.  barometric  pressure, 
l8°  C.  temperature,  saturated  with  moisture.  In  order  to  reduce  it  to  the  normal  state  (760  mm., 
O°  C.,  dry),  we  proceed  as  follows: 

1st.  Look  out  the  degree  18  (columns  I  and  4),  and  deduct  the  tension  of  aqueous  vapor  given, 
j=  15.3  mm.,  from  the  observed  pressure,  —742.0: 

742.0—15.3  =  726.7  mm. 

2d.  Now  find  the  volume  which  I  vol.  of  the  gas  would  have  at  the  pressure  of  726.7  mm. 
by  looking  out  seriatim  the  figures  7,  2,  6,  and  7  in  column  2  at  the  temperature  18°,  and  plating 
the  numerical  values,  to  be  found  opposite  those  figures,  in  the  same  column,  multiplying  them 
seriatim  by  loo,  lo,  I,  o.i ;  whereupon  they  are  added  up,  thus: 

7  0.0086408X100    =0.86408 

2  0.0024688  X    10     =0.024688 

6  0.0074064  x      i     =  0.0074064 

7  0.0086408  X      0.1=0.00086408 

0.89703848 

3d.  The  corrected  volume  of  a  cubic  centimetre  is  lastly  multiplied  by  the  number  of  the  c.c. 
previously  found ;  that  is,  in  the  present  case, 

0.89703848  X  26.2  =  23.502  c.c. 


Tempera- 
ture °  C. 

Pressure 
in  milliras. 
mercury. 

Volume  at  o° 
and  760  mm.  • 

Tension  of  aq. 
vapor  in  millim. 
of  mercury 
for  o  C. 

Tempera- 
ture °  C. 

Pressure 

in  millims. 
mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  mftlim. 
of  mercury 
for°C. 

0 

I 

O.OOI3I57 

0 

6 

0.0078946 

o 

2 

0.0026315 

0 

7 

0.0092104 

o 

3 

0.0039473 

0 

8 

0.0105262 

o 

4 

0.0052631 

O 

9 

O.OII8420 

0 

5 

0.0065789 

o°  =  4-5 

TABLES. 

TABLE  V.— Continued. 


317 


Tempera- 
ture °  C. 

Pressure 
in  millims. 
mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  millim. 
of  mercury 
for  °  C. 

Tempera- 
ture °  C. 

Pressure 
in  millims. 
mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  millim. 
of  mercury 
for  o  C. 

I 

, 

0.0013109 

4 

I 

0.0012965 

I 

2 

O.OO262I9 

4 

2 

0.0025930 

I 

3 

0.0039328 

4 

3 

0.0038895 

I 

4 

0.0052438 

4 

4 

0.0051860 

I 

5 

0.0065548 

i°  =  4-9 

4 

5 

0.0064825 

4°  =  6.0 

I 

6 

0.0078657 

4 

6 

0.0077790 

I 

7 

0.0091767 

4 

7 

0.0090755 

I 

8 

0.0104876 

4 

8 

O.OIO372O 

I 

9 

0.0117986 

4 

9 

0.0116685 

2 

1 

0.0013061 

5 

i 

0.0012916 

2 

2 

0.0026123 

5 

2 

0.0025833 

2 

3 

0.0039184 

5 

3 

0.0038750 

2 

4 

0.0052246 

5 

4 

0.0051667 

2 

5 

0.0065307 

2°  =  5-3 

5 

5 

0.0064584 

5°  =  6.5 

2 

6 

0.0078369 

5 

6 

O.OO775OI 

2 

7 

0.0091430 

5 

7 

0.0090418 

2 

8 

0.0104492 

5 

8 

0-0103335 

2 

9 

0-OH7553 

5 

9 

0.0116252 

3 

i 

0.0013013 

6 

i 

0.0012868 

3 

2 

0.0026026 

6 

2 

0.0025737 

3 

3 

0.0039039 

6 

3 

0.0038606 

3 

4 

0.0052053 

6 

4 

0.0051474 

3 

5 

0.0065066 

3°  =  5-6 

6 

5 

0.0064343 

6°  =  6.9 

3 

6 

0.0078079 

6 

6 

O.OO772I2 

3 

7 

0.0091093 

6 

7 

0.0090080 

3 

8 

O.OIO4IO6 

6 

8 

0.0102949 

3 

9 

O.OII7II9 

6 

9 

0.0145818 

THE    CHEMICAL    ANALYSIS   OF  IRON. 
TABLE  V. — Continued. 


Tempera- 
ture °  C. 

Pressure 
in  millims. 
mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  millim. 
of  mercury 
for  o  C. 

Tempera- 
ture o  C. 

Pressure 
in  millims. 
mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  millim 
of  mercury 
for  °  C. 

7 

I 

0.0012828 

10 

I 

0.0012692 

7 

2 

0.0025656 

10 

2 

0.0025384 

7 

3 

0.0038484 

10 

3 

0.0038076 

7 

4 

0.0051312 

10 

4 

0.0050768 

7 

5 

0.0064140 

7°  =  7-4 

10 

5 

0.0063460 

10°  =  9.  1 

7 

6 

0.0076968 

10 

6 

0.0076152 

7 

7 

0.0089796 

10 

7 

0.0088844 

7 

8 

0.0102624 

10 

8 

0.0101536 

7 

9 

0.0115452 

IO 

9 

O.OII4228 

8 

i 

0.0012783 

II 

i 

0.0012648 

8 

2 

0.0025566 

II 

2 

0.0025296 

8 

3 

0.0038349 

II 

3 

0.0037944 

8 

4 

0.0051132 

II 

4 

0.0050592 

8 

5 

0.0063915 

8°  =  8.0 

II 

5 

0.0063240 

11°  =  9.7 

8 

6 

0.0076698 

II 

6- 

0.0075888 

8 

7 

0.0089481 

II 

7 

0.0088536 

8 

8 

0.0102264 

II 

8 

O.OIOII84 

8 

9 

0.0115047 

II 

9 

0.0113832 

9 

i 

0.0012737 

12 

i 

O.OOI26O3 

9 

2 

0.0025474 

12 

2 

O.OO252O6 

9 

3 

0.0038211 

12 

3 

0.0037809 

9 

4 

0.0050948 

12 

4 

0.0050412 

9 

5 

0.0063685 

9°  =  8.5 

12 

5 

0.0063015 

12°  =  10.4 

9 

6 

0.0076422 

12 

6 

0.00/5618 

9 

7 

0.0089159 

12 

7 

0.0088221 

9 

8 

0.0101896 

12 

8 

O.OIOO824 

9 

9 

0.0114633 

12 

9 

0.0113427 

J 

TABLES. 
TABLE  V.— Continued. 


319 


Tempera- 
ture °  C. 

Pressure 
in  millims. 
mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  millim. 
of  mercury 
for  °  C. 

Tempera- 
ture °  C. 

Pressure 
in  millims. 
mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  millim. 
of  mercury 
for  °  C. 

J3 

I 

0.0012559 

16 

I 

0.0012429 

!3 

2 

O.OO25II8 

16 

2 

0.0024858 

13 

3 

0.0037677 

16 

3 

0.0037287 

13 

4 

0.0050236 

16 

4 

0.0049716 

J3 

5 

0.0062795 

I3°=  II.  I 

16 

5 

0.0062145 

I6°  =  I3.5 

*3 

6 

0.0075354 

1  6 

6 

0.0074574 

*3 

7 

0.0087913 

16 

7 

0.0087003 

13 

8 

0.0100472 

16 

8 

0.0099432 

!3 

9 

0.0113031 

16 

9 

o.oi  11861 

H 

I 

O.OOI25I6 

17 

I 

O.OOI3386 

H 

2 

0.0025032 

17 

2 

O.OO24772 

H 

3 

0.0037548 

17 

3 

0.0037158 

H 

4 

0.0050064 

17 

4 

0.0049544 

H 

5 

0.0062580 

I4°  =  II.9 

17 

5 

0.0061930 

17°  =  14.4 

H 

6 

0.0075096 

J7 

6 

0.0074316 

H 

7 

0.0087612 

17 

7 

O.OO867O2 

14 

8 

O.OIOOI28 

17 

8 

0.0099088 

H 

9 

0.0112644 

17 

0 

O.OIII474 

15 

i 

O.OOI2472 

18 

I 

0.0012344 

15 

2 

0.0024944 

18 

2 

0.0024688 

15 

3 

0.0037416 

18 

3 

0.0037032 

15 

4 

0.0049888 

18 

4 

0.0049376 

15 

5 

0.0062360 

15°  =  12.7 

18 

5 

0.0061720 

180  =  15.3 

15 

6 

0.0074832 

18 

6 

0.0074064 

i5 

7 

0.0087304 

18 

7 

0.0086408 

15 

8 

0.0099776 

18 

8 

0.0098752 

15 

9 

O.OII2248 

18 

9 

O.OIIIO96 

320 


THE    CHEMICAL   ANALYSIS   OF  IRON. 

TABLE  V. — Continued. 


Tempera- 
ture °  C. 

Pressure 
in  millims. 
mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  millim. 
of  mercury 
for°C. 

Tempera- 
ture °  C. 

Pressure 
in  millims. 
mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  millim. 
of  mercury 
for  °  C. 

19 

I 

O.OOI230I 

22 

I 

O.OOI2I76 

J9 

2 

0.0024602 

22 

2 

0.0024352 

19 

3 

0.0036903 

22 

3 

0.0036528 

19 

4 

0.0049204 

22 

4 

0.0048704 

19 

5 

0.0061505 

I9°  =  I6.3 

22 

5 

0.006o88o 

22°=  19.6 

19 

6 

0.0073806 

22 

6 

0.0073056 

19 

7 

O.OO86IO7 

22 

7 

0.0085232 

19 

8 

0.0098408 

22 

8 

0.0097408 

19 

9 

O.OII0709 

22 

9 

0.0109584 

2O 

i 

O.OOI2259 

23 

i 

O.OOI2I35 

2O 

2 

O.OO245I8 

23 

2 

0.0024270 

2O 

3 

0.0036777 

23 

3 

0.0036405 

2O 

4 

0.0049036 

23 

4 

0.0048540 

20 

5 

0.0061295 

20°  r=  17.4 

23 

5 

0.0060675 

23°  =  20.9 

2O 

6 

0-0073554 

23 

6 

0.0072810 

2O 

7 

0.0085813 

23 

7 

0.0084945 

20 

8 

0.0098122 

23 

8 

0.0097080 

20 

9 

O.OIIO33I 

23 

9 

0.0109215 

21 

i 

O.OOI22I8 

24 

I 

O.OOI2O94 

21 

2 

0.0024436 

24 

2 

0.0024188 

21 

3 

0.0036654 

24 

3 

0.0036282 

21 

4 

0.0048872 

24 

4 

0.0048376 

21 

5 

0.0061090 

21°  =18.5 

24 

5 

0.0060470 

24°  =  22.2 

21 

6 

0.0073308 

24 

6 

0.0072564 

21 

7 

0.0085526 

24 

7 

0.0084658 

21 

8 

0.0097744 

24 

8 

0.0096752 

21 

9 

0.0109962 

24 

9 

0.0108846 

TABLES. 
TABLE  V. — Continued. 


321 


T-r7oT  inp=T, 

mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  millim. 
of  mercury 
for  °  C. 

Tempera- 
ture °  C. 

Pressure 
in  millims. 
mercury. 

Volume  at  o° 
and  760  mm. 

Tension  of  aq. 
vapor  in  millim. 
of  mercury 
for  °  C. 

25                    I 

O.OOI2O54 

28 

! 

0.0011933 

25                     2 

0.0024108 

28 

2 

0.0023866 

25 

3 

0.0036162 

28 

3 

0-0035799 

25 

4 

0.0048216 

28 

4 

0.0047732 

25 

5 

0.0060270 

25°  =  23.5 

28 

5 

0.0059665 

28°  —  28.1 

25 

6 

0.0072324 

28 

6 

0.0071598 

25 

7 

0.0084378 

28 

7 

0.008353! 

25 

8 

0.0096432 

• 

28 

8 

0.0095464 

25 

9 

0.0108486 

28 

9 

0.0107397 

26 

i 

O.OOI2OI3 

29 

i 

0.0011894 

26 

2 

O.OO24O26 

29 

2 

0.0023788 

26 

. 

3 

0.0036039 

29 

3 

0.0035682 

26 

4 

0.0048052 

29 

4 

0.0047576 

26 

5 

0.0060065 

26°  =  25.0 

29 

5 

0.0059470 

29°  =r  29.8 

26 

6 

0.0072078 

29 

6 

0.0071364 

26 

7 

0.008409! 

29 

7 

0.0083258 

26 

8 

0.0096104 

29 

8 

0.0095152 

26 

9 

O.OI08II7 

29 

9 

0.0107046 

27 

i 

0.0011973 

30 

i 

O.OOII855 

27 

2 

0.0023946 

3° 

2 

0.0023710 

27 

3 

0.0035919 

30 

3 

0.0035565 

27 

4 

0.0047892 

30 

4 

0.0047420 

27 

5 

0.0059865 

27°  =  26.5 

3° 

5 

0.0059275 

30°  =  31.6 

27 

6 

0.0071838 

3° 

6 

0.0071130 

2? 

7 

0.0083811 

30 

7 

0.0082985 

27 

8 

0.0095784 

30 

8 

0.0094840 

27 

9 

0.0107757 

30 

9 

0.0106695 

INDEX. 


PAGE 

Absorption  apparatus  for  carbon  dioxide  in  car- 
bon determinations 137,  153 

precautions  in  weighing 138 

Acetic  acid,  reagent 40 

Acids  and  halogens 38 

Air-bath 19 

Air-blast  with  Richards's  injector 24 

Alcohol  lamps 23 

Alkalies,  determination  of,  in  clay 279 

determination  of,  in  iron  ores 264 

Alkaline  earths,  salts  of 51 

salts 44 

Allen,  determination  of  nitrogen  in   iion  and 

steel 207 

Alumina  reagent,  in  direct  combustion  of  steel,  135 

Alumina  and  ferric  oxide,  separation  of  ....  257 

by  ammonium  sulphide 257,  276 

by  caustic  potash  or  soda 258 

by  sodium  hyposulphite 198,  259 

by  volatilization  of  the  iron  in  a  cur- 
rent of  hydrochloric  acid  gas  after 

reduction  by  hydrogen     ........  259 

Aluminum,  determination  of,  in  iron  and  steel  196 

Carnot's  method 197 

ether  method 198 

Stead's  method 196 

separation  of,  from  chromium, 194,  198 

Ammonia,  reagent     44 

Ammonium  acetate,  reagent     45 

bisulphite,  reagent 44 

chloride,  reagent 45 

fluoride,  reagent 45 

nitrate,  reagent 45 

oxalate  reagent 46 

quantity  required  in  the  determination 

of  lime  in  limestone 274 

Ammonium  sulphide,  reagent 44 

salts,  decomposition  of,  by  nitric  acid  .    .    .  265 

Apparatus n 

general  laboratory 18 

Arsenic,  determination  of,  as  arsenious  sulphide  199 

as  magnesium  arsenate 200 

by  distillation 199 

in  iron  and  steel 199 

Arsenic  and  antimony,  separation  of,  from  cop- 
per and  lead 262 

Arsenic,  copper,  antimony,  and  lead,  determin- 
ation of,  in  iron  ores 261 

Ash  in  coal  and  coke,  determination  of    ....  290 

Balances 35 

Bamber's  method  for  sulphur  in  pig-it  on     ...  67 
Barba,  asbestos  for  settling  carbonaceous  mat- 
ter in  solutions  of  steel 159 


PAGE 

Barba,  determination  of  chromium  in  steel    .    .  195 

member  of  Sub-Committee  on  Methods    .   .  92 

Barium  acetate,  reagent 51 

carbonate,  reagent 51 

chloride,  reagent 51 

determination  of,  as  sulphate  in  iron  ores  250 

hydroxide,  reagent 52 

Baryta,  caustic,  reagent 52 

caustic,  standard  solution  of,  for  determina- 
tion of  methane 307 

Berzelius,  determination  of  carbon  in  iron  and 

steel 133 

determination  of  sulphur  in  iron  and  steel  63 
Boat  of  platinum-foil  for  determination  of  carbon 

in  iron  and  steel 164 

Britton,  permanent  standards  for  color-carbon 

method 182 

Bromine,  reagent 4° 

Bromine- water  for  absorbing  ethylene 304 

Bunsen  burners 21 

chimneys  for 22 

Bunsen,  determination  of  manganese  dioxide  in 

iron  ores 246 

Bunsen's  method  of  rapid  filtration 25 

Calcium  carbonate,  reagent 52 

chloride,  reagent 52 

Camera,  for  use  in  color-carbon  method  ....  181 

Caps  for  reagent  bottles 31 

Carbon,  determination  of,  in  chrome-tungsten 

steels 2ii 

Carbon,  determination  of,  in  ferro-chrome  .   .  217 
determination  of  in  ferro-tungsten  and  tung- 
sten metal 215 

in  iron  and  steel 132 

in  carbonaceous  matter,  determination 

of,  in  iron  ores 267 

Carbon,  combined,  determination  of,  in  iron  and 

steel  by  color  method 175 

determination  of,  in  white  cast  iron 

and  p'g  iron 183 

Carbon,  determination  of,  by  direct  method  .   .  175 

by  indirect  method 175 

limitations  of  color  method    ....  176 

Carbon,  fixed,  determination  of,  in  coal  ....  290 
Carbon,  total,  determination  of,  in  iron   and 

steel 132 

by  combustion  in  the  Shimer  crucible  171 
by  combustion  with  copper  oxide  in  a 

current  of  oxygen 145 

by  combustion  with  lead  chromateand 

potassium  chlorate 143 

by  direct  combustion  in  a  Gooch  tubu- 
lated crucible 139 


323 


324 


INDEX. 


PAGE 

Carbon,  by  direct  combustion  in  oxygen  .   .   .      134 
by  solution  and  oxidation  of  the  bor- 
ings   by    sulphuric,    chromic,  and 
phosphoric  acids,  the  carbon  diox- 
ide being  measured 146 

by  solution  and  oxidation  of  the  bor- 
ings by  sulphuric,  chromic,  and 
phosphoric  acids,  the  carbon  diox- 
ide being  weighed 149 

by  solution  in  copper  sulphate,  and 
combustion  of  residue  by  chromic 

and  sulphuric  acids 174 

by  solution  in  cupric  sulphate,  and 
combustion  of  residue  in  a  current 

of  oxygen 173 

by      solution       in      potassium-cupric 
chloride,    and     combustion    of 

residue 156 

modification  of   (Job  and  Davies)     166 
by  volatilization  in  a  current  of  chlo- 
rine, and  combustion  of  residue   .   .      151 
by  volatilization  in  a  current  of  hydro- 
chloric acid  gas,  and  combustion  of 

residue 156 

Carbonic  acid  gas,  reagent 42 

absorbent  for 300 

apparatus  for  generating 61 

determination  of,  in  gases 302 

determination  of,  in  iron  ores    ....      265 
purifying  and  drying  apparatus  for, 
in  carbon  determinations     .   .    .  153,     161 

Carbonic  oxide  gas,  absorbent  for ;,oi 

absorption  of,  by  cuprous  chloride  .   .      301 
determination  of,  in  gases   ....  304,    306 
Carnot,  determination  of  aluminum  in  iron  and 

steel 197 

determination  of  nickel  in  steel 188 

Chase,  determination  of  nickel 191 

Chimneys  for  Bunsen  burners 22 

Chlorine,  reagent 41 

Chrome  iron  ore,  analysis  of 271 

Chrome-tungsten-steels,  methods  for  the  analy- 
sis of     211 

Chromic  acid,  reagent 42 

Chromium,  determination  of,  in  ferro-chrome    220 
determination  of,  in  chrome-tungsten 

steels 212 

determination  of,  in  iron  and  steel  .   .      193 

ether  method 194 

determination  of,  in  iron  ores  ....  270 
separation  of,  from  aluminum,  194, 198,  271 
volumetric  method  for  determ. nation 

of,  in  iron  and  steel 194 

Chromium    and    vanadium,  separation    of,    in 

chrome-tungsten  steels 214 

Chromium  and  aluminum,  separation  of,  from 

phosphoric  acid 271 

Cinder,  mill  and  tap,  analysis  of 285 

Citric  acid,  reagent 40 

Clay,  methods  for  the  analysis  of 278 

Coal,  calorific  power  of    .   .. 295 


Coal,  determination  of  sulphur  in 

heating  effect  of 

proximate  analysis  of 

ultimate  analysis  of 

Coal  and  coke,  methods  for  the  analysis  of 
Cobalt,  determination  of,  as  sulphate  .  .  . 

determination  of,  by  electrolysis  .    .    . 


PAGE 

290 
295 
288 
294 
288 
I89 
190 

Cobalt  and  nickel,  determination  of,  in  iron  and 

steel 188 

Coke,  determination  of  sulphur  in 290 

Combined  water,  determination  of,  in  iron  ores^  267 

Committee  on  Coal  Analysis,  reference  to   ...  288 

Comparison-tubes  for  color-carbon  method     .   .  180 

Cone,  Hooch's  perforated 28 

Copper,  determination  of,  as  cupric  oxide  .   .    .  188 

as  cuprous  sulphide 188 

by  electrolysis 186 

by  precipitation  by  sodium  hyposulphite  187 

anhydrous  sulphate,  reagent 53 

metallic,  reagent 53 

oxide,  reagent 55 

sulphate,  reagent 53 

Copper  and  ammonium,  double  chloride  of,  rea- 
gent   54 

and  potassium,  double  chloride  of,  reagent  54 
repeated  use  of,  for  solution  of  iron  and 

steel 170 

Copper,  lead,  arsenic,  and  antimony,  determina- 
tion of,  in  iron  ores 261 

Counterpoised  filters 28 

Craig,  determination  of   sulphur    in  iron  and 

steel .;.   .  65 

Crucibles 32 

Gooch's  perforated 27 

Crucible-tongs,  forms  of 34 

Cupric  chloride,  reagent 54 

Cuprous  chloride,  anhydrous,  reagent 54 

reagent,  for  absorbing  carbon  monoxide  301 

Davies,  carbon  in  iron  and  steel 166 

Deshays,  determination  of   manganese  in  iron 

and  steel '  .  .  128 

Desiccators 32 

Deville,  determination  of    carbon  in  iron  and 

steel 133 

Dishes,  platinum     . 33 

Distilled  water 37 

apparatus  for  making .  .  . -v  •   •  37 

Drill-press 15 

Drill-press  for  holding  half  a  pig  of  iron  ....  15 

Drill-press  and  bala.ice 61 

Drown,  determination  of  silicon  in  pig-iron    .   .  73 

determination  of  sulphur  in  iron  and  steel  65 

determination  of  titanium  in  iron     ....  185 
member  of  Sub-Committee  on  Standard 

Methods 92 

Drying   and  purifying    apparatus    for    carbon 

dioxide  in  carbon  determinations 153,  161 

Dubois  and  Mixer,  determination  of  iron  in  iron 

ores 229 

Dudley,  chairman  Sub-Committee  on  Standard 

Methods 92 


INDEX, 


325 


PAGE 

Eggertz,  determination  of  combined  carbon  in 

iron  and  steel i?5 

determination  of  phosphorus  in  iron  and 

steel 90 

Elliott,  determination  of  sulphur  in  iron  and 

steel 63 

Eschka,  determination  of  sulphur  in  coal  and 

coke 291 

Ethylene,  absorbent  for 302 

determination  of,  in  gases 304 

Factor  weights 36 

Feather  for  removing  precipitates 31 

Ferric  chloride,  solution  of,  for  standardizing 

solutions  cf  permanganate  and  bichromate  .   .  230 

Ferro-chrome,  determination  of  carbon  in  ...  217 
Ferro-tungsten  and  tungsten  metal,  methods  for 

the  analysis  of 215 

Ferrous-oxide,  determination  of,  in  iron  ores  .   .  233 

Ferrous  sulphate,  reagent 56 

Ferrous-ammonium  sulphate,  reagent 56 

Filtering-tubes  for    carbon    determinations    in 

iron  and  steel 162 

Filter-paper 29 

Filter-pumps 24 

Filters,  ashless 29 

Filtration,  Bunsen's  method  of 25 

Fire-sands,  method  for  analysis  of 287 

Forceps  for  use  in  carbon  determinations  in  iron 

and  steel 161 

Ford,  determination  of  manganese  in  iron  and 

steel 113 

rapid  method  for  determination  of  silicon  in 

pig-iron 77 

Fresenius,  determination  of  phosphorus  in  iron 

and  steel     80 

determination  of  sulphur  in  iron  and  steel  64 
Galbrailh,  volumetric  method  for  determination 

of  chromium  in  iron  and  steel 194 

Gas,  Siemens's  producer,  example  of  analysis  of  310 

Gases,  analysis  of,  by   Hempel's  apparatus  .    .  302 

collecting  samples  of,  for  analysis 297 

methods  for  the  analysis  of 297 

rengents 42,  300 

Glass  filtering-tube  for  carbon  determinations  in 

iron  and  steel 162 

Gooch,  separation  of  titanic  acid  and  alumina  241 

Gooch's  method  of  rapid  nitration 27 

perforated  crucible  and  cone 27 

tubulated  crucible 268 

Graphitic  carbon,  determination  of,  in  iron  and 

steel • 174 

Handy,   determination  of  phosphorus  in  iron 

and  steel 104 

Hempel's  apparatus  for  the  analysis  of  gases  297 

Hogarth,  specific-gravity  flask 273 

Hydrochloric  acid,  reagent 38 

Hydrofluoric      acid,    apparatus    for    distilling,  39 

reagent 39 

Hydrogen,  combustion   of,  with   spongy  palla- 
dium       304 

gas,  apparatus  for  generating 61 


PAGE 

Hydrogen  sulphide  gas 43 

apparatus  for  generating 61 

Hygroscopic  water.determination  of,  in  iron  ores  223 

Igniting  precipitates 22 

Insoluble  silicious  matter  in  iron  ores,  analysis 

of 249 

Iodine,  reagent 41 

Iron,  determination  of,  in  ferro-chrome,  ferro- 

silicon,  and  ferro-titanium 221 

determination  of  metallic,  in  iron  and  steel  210 
Iron,  total,  determination  of,  in  iron  ores     .   .   .  224 
by  deoxidation  by  ammonium  bi- 
sulphite    227 

by  deoxidation  by  stannous  chlo- 
ride     228 

by  deoxidation  b.  zinc 225 

by  standard  solution  of  potassium 

bichromate 226 

by  standard  solution  of  potassium 

permanganate 226 

Iron  ores,  method  of  sampling 222 

Iron  wire,  reagent 55 

Iron  and  ammonium,  double  sulphate  of,  rea- 
gent   «  56 

Job,  carbon  in  iron  and  steel 166 

Karsten,  determination  of   graphitic  carbon  in 

pig-iron 174 

determination  of  sulphur  in  iron  and  steel  60 
Kudernatsch,  determination  of  carbon  in  iron 

and  steel 133 

Langley,  determination  of  carbon  in  iron  and 

steel 133 

determination  of  nitrogen  in  iron  and  steel  207 
Lead,  determination  of,  as  lead  sulphate  in  iron 

ores 262 

chromate,  reagent 57 

oxide,  dissolved  in  caustic  potash  .   ...  58 

peroxide,  reagent 57 

Lead,  copper,  arsenic,  and  antimony,  determina- 
tion of,  in  iron  ores 261 

Limestone,  methods  for  the  analysis  of    ....  274 

occasional  constituents  of 275 

Lundin,  determination  of  arsenic  in  iron  and 

steel 199 

Magnesia,  determination  of,  in  iron  ores  ....  250 

in  limestones 275 

Magnesia-mixture,  reagent 59 

Manganese,  dioxide  of,  in  iron  ores 245 

Manganese,    determination     of,    by    Bunsen's 

method 246 

by  ferrous  sulphate  method    .   .  247 
determination  of,  as  manganese  pyrophos- 

phate in 

as  manganoso-manganic  oxide  .   ...  in 

as  manganous  sulphide 112 

determination     of,     in     chrome-tungsten 

steels 212 

determination  of,  in  ferro-chrome,  ferro- 

silicon,  and  ferro-titanium 220 

determination   of,   in   iron   and   steel,   by 

acetate  method   .                 108 


326 


INDEX. 


PAGE 

Manganese,  by  bismuthate  method 121 

by  Deshays's  method 128 

by  nitric  acid  and  potassium  chlorate 

(Ford's  method) 113 

by  Volhard's  method 116 

by  Williams's  method 118 

in  presence  of   much  silicon  (Wood's 

method) 115 

rapid  methods 116 

remarks    on     ths     use     of      acetate 

method     .       112 

determination  of ,  in  iron  ores 242,  260 

by  bismuthate  method 123 

by  Pattinson's  method 246 

by  Volhard's  method 246 

determination  of,  in  pig-iron  by  bismuth- 
ate  method 122 

determination  of,  in  pig-iron,  spiegel  and 

ferro- manganese,  by  Ford's  method  .   .  115 
determination  of,  in  spiegel    and    ferro- 

manganese 120 

by  bismuthate  method 124 

by  Williams's  method 120 

determination    of    in  steel,  by    the    color 

method 129 

Walter's  modification   ....  131 
in  presence  of  much  silicon  (Ford's 

method) 115 

Marguerite's  method  for  determination  of  iron  226 
Matthewman,  determination  of  sulphur  in  pig- 
iron    67 

Measuring-glasses  for  reagents 31 

Mercuric  oxide,  reagent 57 

Mercurous  nitrate,  reagent 56 

Metals  and  metallic  salts,  reagents 53 

Methane,  determination  of,  in  gases 307 

Microcosmic  salts,  quantity  necessary  in  the  de- 
termination of  magnesia  in  lime- 
stones    ...  .  275 

reagent 46 

Mixer  and  Dubois,  determination  of  ircn  in  iron 

ores 229 

Moisture  in  coal,  determination  of 288 

Molybdate  solution,  reagent 59,  97 

Molybdenum,  determination  of,  in  ferro-molyb- 

denum 206 

determination  of,  in  iron  and  steel 205 

rapid  method  for  determination  of 206 

Morrell,  determination  of  sulphur  in  iron  and 

steel 63 

Mortar,  agate,  with  Stow  flexible  shaft  ....  13 
agate,  White's    arrangement    to    use   with 

power 14 

hardened  steel,  for  spiegel 17 

Mortar  and  pestle,  steel,  for  crushing  ores  ...  12 

Muffles 23 

Nessler,  reagent  for   nitrogen    determinations  208 
Nichols,  details  of  rapid  method  for  determina- 
tion of  phosphorus  in  iron  and  steel 106 

Nickel,  determination  of,  as  nickel  sulphide  or 

nickel  oxide 190 


PAGE 

Nickel,  determination  of,  by  ether  method  .    .    .  191 

separation  of,  from  cobalt 189 

Nickel  and  cobalt,  determination  of,  by  elec- 
trolysis      190 

determination  of,  in  iron  and  steel  ...  188 
determination    of,    in    chrome-tungsten 

steels 213 

separation  of,  from  copper 189 

Nickel,  ch:omium,  and  manganese,  determina- 
tion of,  in  chrome-tungsten  steels 213 

Nickel,  cobalt,  zinc,  and  manganese,  determi- 
nation of,  in  iron  ores, .."...  260 

Nickel,  steel  analysis  of .  .  .  190 

Nitric  acid,  reagent 38 

Nitrogen,  determination  of,  in  gases 309 

determination  of,  in  iron  and  steel 207 

Oxalic  acid,  reagent 40 

standard  solution  of,  for    determina- 
tion of  methane 307 

Oxygen,  absorbent  for 294 

determination  of,  in  gases 304 

gas,  reagent 43 

Pan,  aluminum,  for  weighing  samples 36 

Penny's  method  for  determination  of  iron  .    .    .  226 
Perforated  boat  and  holder  for  filtering  carbo- 
naceous residues  from  iron  and  steel     ....  159 
Permanent  standards  for  color-carbon  determi- 
nations       182 

Peters,  determination  of  manganese  in  steel  by 

color  method 129 

Phillips,  determination  of  sulphur  in  pig-iron  67 
Phosphoric  acid,  determination  of,  in  coal  and 

coke 293 

in  iron  ores 23 ) 

in  limestone 276 

in  slags 286 

Phosphorus,  determination  of,  in  ferro-chrome  219 
determination     of,    in     chrome-tungsten 

steels 212 

in  ferro-silicon 219 

in  ferro-titanium 220 

ia  ironand  steel 80 

alkalimetric  method 104 

by  direct  weighing  of  phospho- 

molybdate 106 

by  the  acetate  method 80 

by  the  acetate  method,  precau- 
tions necessary 82,  84 

by  the  combination  method    .    .  91 

Phosphorus,  by  the  molybdate  method 88 

by  the  molybdate  method,  pre- 
cautions necessary  91,92 

by  the  volumetric  method 
(method  of  the  Sub-Committee 
on  Methods  of  the  Interna- 
tional Steel  Standards  Com- 

mittte)     92 

by  rapid  methods    .......  92 

when  titanium  is  present  85,  92 
as   ammonium  phospho-  molyb- 
date    91 


INDEX. 


327 


PAGE 

Phosphorus,    as     magnesium     pyrophosphate  85 
determination    of,   in   iron  and    steel,  as 
magnesium    pyrophosphate  with  previ- 
ous   precipitation     as    phosphomolyb- 

date 9° 

separation  of,  from  arsenic 82,  91 

Phospho-titanate,  insoluble 85 

Pichard,  determination  of  manganese  in  steel 

by  the  color  method 129 

Pipette,  Hempel's  composite,  method  of  filling  301 

Hempel's  simple,  method  of  filling     .    .    .  300 

Plate,  chilled  iron,  and  muller 12 

Platinic  chloride  solution,  reagent 58 

Platinum  apparatus 32 

combustion-tube    for    carbon    determina- 
tions in  iron  and  steel 135 

crucibles,  method  of  cleaning 32 

filtering-tube  for  carbon  determinations  in 

iron  and  steel 162 

"  Policemen  "  for  removing  precipitates  ....  31 

Potash  and  soda,  separation  of 264 

Potassium  bichromate,  reagent 48 

bisulphate,  reagent 49 

chlorate,  reagent 49 

ferricyanide,  reagent 5° 

ferrocyanide,  reagent 50 

hydroxide,  reagent 47 

iodide,  reagent 50 

nitrate,  reagent 48 

nitrite,  reagent 47 

permanganate,  reagent 5° 

sulphide,  reagent 48 

Potassium    permanganate   solution,    methods 

of  standardizing 96,  229 

standard  solution  of,  for  determination 

of  iron 233 

Potassium  pyrogallate,  absorbent  power  of    .   .  301 

Purifying  apparatus  for  oxygen  and  air  ....  136 
Rack  for  permanent  standards  in  color-carbon 

method 182 

Rapid  evaporations,  apparatus  for 20 

Rapid  filtration,  Bunsen's  method  of 25 

Gooch's  method  of 27 

Reagents 37 

for  determining  phosphorus 59 

for  the  analysis  of  gases 300 

Reductor,  simple  form  of 94 

Regnault,  determination  of  carbon  in  iron   and 

steel 133 

Removing  precipitates  from  beakers 30 

Richards  injector 24 

Richter,  determination  of    carbon  in  iron  and 

steel 133 

Riley,  determination  of  titanium  in  pig-iron   .   .  184 

Rivot,  separation  of  alumina  and  ferric  oxide  .   .  259 

Kose,  separation  of  alumina  and  ferric  oxide  .   .  258 

Rothe,  determination  of  nickel  in  steel     ....  191 

determination  of  chromium  in  steel    .       .  193 

Rubber  stoppers 32 

Safety-guard  tube  in  carbon  determinations  .   .  137 

Sampling  iron  ores,  method  of 222 


PAGE 

Sampling  iron  ores,  pig-iron,  method  of  ....  15 

Sand-bath 18 

Sargent,  rechlorinated    double    chloride    solu- 
tion      169 

Shimer  crucible,  determination   of  carbon    by 

combustion  of  residue  in 171 

member     Sub-Committee    on     Standard 

Methods 92 

insolubility  of  titanium  carbide  in  hydro- 
chloric acid       175 

Siemens's  producer  gas,  example  of  analysis  of  3:0 

Silica,  determination  of,  in  iron  ores     ....  249,  256 
Silica,  alumina,    lime,    magnesia,    manganese 
oxide,  and  baryta,  determination  of  in  iron 

ores 248 

Silicon,  determination  of,  in  ferro  silicon,  ferro- 

chrome,  etc 218 

in  chrome-tungsten  steels      211 

determination  of,  in  iron  and  steel  ....  72 
by  solution  in  nitric  and  hydrochlo- 
ric acids 72 

by  volatilization  in    a    current    of 

chlorine 73 

determination  of,  in    pig-iron,    Drown's 

method 73 

rapid  method,  by  Ford 77 

Slag  and  oxides,  determination  of,  in  iron  and 

steel 78 

by  solution  in  iodine 78 

by  volatilization  in  a  current  of 

chlorine  gas 80 

Slag,  basic,  analysis  of .  285 

converter,  analysis  of 285 

Slag  decomposed  by  hydrochloric  acid,  analy- 
sis of     283 

not  decomposed     by     hydrochloric     acid, 

analysis  of 285 

Slag  refinery,  analysis  of 285 

Slags,  methods  for  the  analysis  of 283 

Smith,  J.  L.,  determination  of  alkalies  in  min- 
erals    280 

Soda  and  potash,  separation  of 264 

Sodium  acetate,  reagent 47 

bismuthate,  method  of  making 121 

carbonate,  reagent 46 

hyposulphite,  reagent      47,  69 

nitrate,  reagent 47 

thiosulphate,  reagent 47,  69 

Sodium-ammonium  phosphate,  reagent    ....  46 

Sodium  hydroxide,  reagent 46 

Sonnenschein,  determination  cf  phosphorus  in 

iron  and  steel 88 

Spatulas,  platinum 34 

Specific  gravity  of  iron  ores,  method  of  deter- 
mining       272 

flask  for 273 

Stand  for  holding  absorption  apparatus  for  car- 
bon dioxide  in  the  determination  of  carbon  in 

iron  and  steel IJJB 

Standard  solutions  for  determination  of  iron, 

proper  strength  of 233 


328 


INDEX. 


PAGE 

Standardizing  volumetric  solutions  for  deter- 
mination of  iron  by  ferrous  sulphate  232 

by  iron  wire 96,  232 

by  solution  of  ferric  chloride    ....      230 

Starch  solution,  reagent 69 

Stead,  determination  of  aluminum  in  iron  and 

steel 196 

Stirring  machine  for  dissolving  steel  and  iron  in 

carbon  determinations 157 

Sulphates,  soluble,  determination  of,  in  iron  ores    238 

Sulphur,  conditions  of,  in  coal 293 

as  sulphides,  in  iron  ores 237 

determination     of,     in     chrome-tungsten 

steels 211 

determination    of,  in  ferro-tungsten  and 

tungsten  metal 216 

determination  of,  in  ferro-chrome,  ferro- 

silicon,  and  ferro-titanium 217 

determination  of,  in  iron  and  steel  by  evo- 
lution as  hydrogen  sulphide  ...       60 
by  evolution  as  hydrogen  sulphide 
and  absorption  by  alkaline  solu- 
tion of  lead  nitrate 60 

Sulphur,  determination  of,  in  iron  and  steel 
by  evolution  as  hydrogen  sulphide 
and  absorption  by  ammoniacal  solu- 
tion of  cadmium  sulphate 63 

by  evolution  as  hydrogen  sulphide 
and  absorption  in  ammoniacal  solu- 
tion of  silver  nitrate 63 

by  evolution    as    hydrogen    sulphide 

and  absorption    and    oxidation    by 

bromine  and  hydrochloric  acid     .   .       64 

by  evolution    as    hydrogen  sulphide 

and  absorption    and    oxidation  by 

hydrogen  peroxide 65 

by  evolution  as  hydrogen  sulphide 
and  absorption  and  oxidation  by 

potassium  permanganate 65 

by  rapid  method 68 

determination  of,  in  coal  and  coke     .   .    .      290 
determination    of,  in  pig-iron,  Bamber's 

method 67 

special  precautions 67 

total,  determination  of,  in  iron  ores    ....      237 
method  of    reporting   amount   of,    in 

coal 293 

Sulphuric  acid,  reagent 39 

Sulphurous  acid,  reagent 41 

Svanberg  and  Struve,  phospho-molybdate  reac- 
tion           88 

Tartaric  acid,  reagent 40 

Tin,  determination  of,  in  iron  and  steel    ....      200 

Titanic  acid,  determination  of,  in  clay 281 

determination  of,  in  iron  ores   ....      241 
interference  of  phosphoric  acid  with 

precipitation  of 241 

iron  ores  containing 240 

analysis  of 240 

separation  of,  from  phosphoric  acid    241 
tests  for,  in  iron  ores 240 


Titaniferous  iron  ores,  method  of  recognizing  240 

Titanium,  determination  of,  in  iron is; 

by  precipitation 184 

by  volatilization      185 

Triangles  and  tripods  of  platinum 34 

Tripods 22 

Tungsten,  determination  of,  in  iron  and  steel  201 

in  chrome-tungsten  steels 211 

in  ferro-tungsten  and  tungsten  metal  215 

in  iron  ores 272 

rapid  method  for  determination  of,  in  iron 

and  steel 202 

Uehling,  apparatus  for  delivering  constant  vol- 
umes of  ferrous  sulphate  solution    ....  120 
apparatus  for  delivering  different  volumes 

of  nitric  acid     178 

Ullgren,  determination  of  carbon  in  iron  and 

steels ,33 

Vanadium,  determination  of,  in  chrome-tungsten 

steels 213 

Vanadium,  determination  of,  i.i  iron  and  steel  202 

determination  of,  in  iron  ores 272 

Vanadium  and    chromium,    separation    of,    in 

chrome-tungsten  steels 214 

Volatile  combustible  matter  in  ccal,  determina- 
tion of 289 

Volhard,  determination  of  manganese  in  iron 

and  steel n6 

in  high  grade  manganese  ores 24; 

Washing-bottles,  forms  of 29 

Watch-glasses,  balanced 36 

Water   of    composition,    determination    of,    in 

clays '".   .   .  281 

in  ir  :m  ores 267 

Water-bath,  for  determination  of  hygroscopic 

water  in  iron  ores       223 

for  use  in  coloi-caibon  method  and  color- 
manganese  method 177 

Watts,  determination  of  silicon  in  iron  and  steel  75 
Whitfie'.d,  apparatus  for  hastening  evaporations  20 
Williams,  method  for  determination  of  manga- 
nese in  iron  and  steel    118 

Wohler,  determination  of  carbon  in  iron  and 

steel 133 

separation  of  alumina  and  ferric  oxide  ...  259 
Wood,  modification  of  color-carbon  method  for 

low  steels 180 

modification  of  rapid  method  for  sulphur 

in  iron  and  steel 71 

rapid  method  for  determination  of  phos- 
phorus in  iron  and  steel 106 

Wood,  use  of  hydrofluoric  acid  in  steels  high  in 
silicon,  and  in  pig-irons,  in  determination  of 

manganese 115 

Zimmerman,  determination  of  iron  in  iron  ores  228 

Zinc,  determination  of,  in  iron  ores 260 

metallic,  reagent 58 

amalgamated  for  use  in  reductor  .   .  97 
powdered    for     reducing    molybdic 

acid 99 

oxide  in  water,  reagent 58 


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